Swimming Pool Codes - City of Fargo

OPERATIONALSTANDARDS FORSWIMMING POOLSFargo Cass Public Health401 3 rd Ave NFargo North Dakota 5810206/26/09

TABLE OF CONTENTSFORWARD………………………………………………………………………………...1Chapter 1 - Laws and Regulations .......................................................................................21.1 Maintenance and Operation of Public Water WorksSystems, Swimming Pools, and Sewage Systems;Regulation by Health Department .............................................................................21.2 Submission of Construction Plans and Specifications Required ...............................21.3 Approval of Construction Plans and Specifications ..................................................21.4 Inspection of Swimming Pools ..................................................................................2A. Pool Facilities in Fargo, North Dakota ................................................................3Chapter 2 - Operational Practices ..........................................................................................42.1 Bacterial Testing ........................................................................................................42.2 Keeping Records ........................................................................................................42.3 Personnel ....................................................................................................................42.4 Bathhouse ...................................................................................................................52.5 Footbaths ....................................................................................................................52.6 Showers ......................................................................................................................52.7 Regulations ................................................................................................................52.8 Pool Safety .................................................................................................................6Chapter 3 – Water Chemistry ................................................................................................73.1 pH ...............................................................................................................................73.2 Adjusting pH ..............................................................................................................73.3 Alkalinity ...................................................................................................................83.4 Adjusting Alkalinity...................................................................................................83.5 Hardness .....................................................................................................................93.6 Adjusting Hardness ....................................................................................................9Chapter 4 – Disinfection ........................................................................................................104.1 Chlorine......................................................................................................................104.2 Chlorine Gas ..............................................................................................................124.3 Calcium Hypochlorite ................................................................................................134.4 Sodium Hypochlorite .................................................................................................144.5 Stabilizer ....................................................................................................................144.6 Bromine......................................................................................................................154.7 Ozone .........................................................................................................................154.8 Ultraviolet ..................................................................................................................154.9 Iodine .........................................................................................................................16Chapter 5 – Recirculation System..........................................................................................175.1 Hair and Lint Strainer ................................................................................................175.2 Pumps .........................................................................................................................17i

5.3 Sand filters .................................................................................................................185.4 High-Rate Sand Filters ...............................................................................................205.5 Diatomaceous Earth Filters ........................................................................................205.6 Cartridge Filters .........................................................................................................225.7 Length of Operation ...................................................................................................23Chapter 6 – Special Conditions..............................................................................................246.1 Swimming Pool Start-up ............................................................................................246.2 Pool Temperature .......................................................................................................246.3 Wind Protection .........................................................................................................246.4 Pool Bottom ...............................................................................................................256.5 Surface Film ...............................................................................................................256.6 Hard Water Scale .......................................................................................................256.7 Iron Removal .............................................................................................................266.8 Organic Color.............................................................................................................266.9 Cloudy Water .............................................................................................................266.10 Algae Control .............................................................................................................276.11 Insects ........................................................................................................................286.12 Painting ......................................................................................................................28Chapter 7 – Special Pools ......................................................................................................307.1 Wading Pools .............................................................................................................307.2 Spas ............................................................................................................................307.3 Natural Bathing Areas................................................................................................31Appendix ................................................................................................................................331 Off Season Protection ................................................................................................332 Pool Loading – Indoor & Outdoor Pools ...................................................................343 Chemical Dosage .......................................................................................................354 Superchlorination .......................................................................................................375 Chlorinator Settings ...................................................................................................386 Safety Rules for Gas Chlorine Equipment .................................................................387 Dechlorination............................................................................................................398 Testing Chlorine Residuals ........................................................................................399 Testing pH ..................................................................................................................4010 Bacteriological Testing ..............................................................................................4011 Enclosure for Swimming Pool Chlorinators ..............................................................4112 Injector Location for Vacuum-Operated Chlorinators ...............................................4213 Recommended Swimming Pool Operations Standards .............................................44ii

FORWARDThis manual has been prepared to aid swimming pool operators, design engineers, and otherinterested persons in the construction and operation of a swimming pool following goodpublic health practices. Proper swimming pool design and operation protects the batheragainst:1. Infections transmitted through the pool.2. Infections transmitted through the bathhouse facilities.3. Physical injury within and about the pool.Definite epidemiological evidence has been recorded to show transmission of infectiousdiseases through pool waters. Definite proof of the transmission of eye infections, impetigo,etc. through the common bathroom is also known. Dermatitis, such as athlete’s foot, iscommonly transmitted in bathing facilities.The primary responsibility of the swimming pool manager is to provide clean, healthfulrecreation. Rules must be understood and followed. Only safe equipment should be broughtinto the pool environment.Another responsibility of the pool operator or owner is that of protection against physicalinjury within and about the pool area. The attendants should have full charge of the bathingfacilities and have the authority to enforce rules of safety and sanitation. Only qualifiedlifeguards should be employed.We believe that if the operational practices outlined in this manual are observed, yourswimming pool can serve as a healthful source of recreation.1

CHAPTER 1 - LAWS AND REGULATIONS1.1 Maintenance and Operation of Public Water Works Systems, Swimming Pools,and Sewage Systems; Regulation by Health Department. For the protection ofpublic health and the prevention of pollution of waters, all public water workssystems, swimming pools, and sewage systems shall be maintained and operated inaccordance with applicable public health standards, codes, and regulations. Thehealth department, and agents and employees thereof, shall have authority to regulate thepublic health and safety in the city of Fargo concerning use, design, operation, andmaintenance of swimming and wading pools and shall have such authority to adoptregulations, rules, standards and practices. Such regulations, rules, standards, andpractices shall be approved by the board of city commissioners, are hereby adopted byreference and fully incorporated herein, including any amendments hereinafter adopted,and shall be controlling within the jurisdiction of the health department. FargoMunicipal Code § 13-1002.1.2 Submission of Construction Plans and Specifications Required. Before work orconstruction is commenced on any water works system, sewage system, or public orsemi-public swimming pool, or for any alteration, addition, remodeling or otherimprovement thereof, the plans specifications, and any other pertinent informationshall be submitted to FARGO CASS PUBLIC HEALTH for review prior toconstruction. Residential swimming pools are exempt from this requirement, butmust meet fencing requirements and other design standards adopted by the healthdepartment and approved by the board of city commissioners.1.3 Approval of Construction Plans and Specifications. Plans and specificationsreviewed by FARGO CASS PUBLIC HEALTH will be approved only when such plansand specifications fully meet and comply with existing statutes, local rules, andapplicable sanitary standards. Plans and specifications upon which approval is beingwithheld will be returned with the reasons for withholding approval.1.4 Inspection of Swimming Pools. The health department may inspect or cause to beinspected all public or semi-public swimming pools and family residential pools withinthe city at such times as it may deem necessary to carry out the intent of this ordinance.The health department is hereby authorized to enter upon any premises, private orpublic, to take such samples of water from such pools at such times as it may deemnecessary and to require the owner, proprietor or operator to comply with rules andregulations pertaining to swimming pools promulgated by the health department inaccordance with this ordinance., and as approved by the board of Fargo citycommissioners. In the event of the failure of compliance after due notice with the rulesand regulations and requirements of the health department or the requirements of thisordinance, the health department shall have the power to abate or cause a suspension ofthe use of such public or semi-public swimming pool or family residential pool untilsuch time as the same is, in the opinion of the health department, no longer a menace ora hazard to health, safety or morals.2

A. POOL FACILITIES IN FARGO, NORTH DAKOTAAll public and semi-public pool facilities are also required to adhere to therule as set forth in Article 13-10 of the Fargo Municipal Code. The primaryaim of these rules is to regulate the water quality and record keeping practicesof public and semi-public pool facilities. Following is a brief synopsis of therules:(i)(ii)(iii)(iv)Routine Bacteriological Sampling: The owner or operator is requiredto sample the microbiological water quality of the pool facility at leastonce per week for public pools and once monthly for semi-publicpools. Public pool facilities, which are open for a full year, maysubstitute 50 percent of the required microbiological water sampleswith pH and free chlorine residual test results.Record Maintenance: The owner or operator of a pool facility shallmaintain records of microbiological analysis, all pool relatedcorrespondence, plus documentation of daily operation andmaintenance practices for a minimum of 3 years.Turbidity/Clarity Requirements: Swimming pool water must havesufficient clarity at all times so that the main drain or drains located atthe deep end of the pool are clearly visible from the pool decking.Disinfectant Residual: All pool facilities shall disinfect the pool waterby continuous chlorination or other means or methods of equalbactericidal efficiency. A minimum of free chlorine residual of 1.0milligrams per liter (mg/l) or a department approved halogen orcompounds of them, imparting an equivalent disinfecting residualmust be maintained in the water at all times.3

2.1 BACTERIAL TESTINGCHAPTER 2 - OPERATIONAL PRACTICESAll public and semi-public pool facilities must meet microbiological water qualityrequirements. To meet these requirements, a microbiological water sample must be collectedonce weekly from public and once monthly from semipublic pool facilities during theirperiod of operation. A satisfactory sample is one that does not show greater than 200bacterial colonies per one milliliter of sample and does not show the presence of the coliformgroup in a fermentation tube or membrane filter test. All samples must be submitted to alaboratory which has been certified by this department.2.2 KEEPING RECORDSFargo Cass Public Health requires that a daily operational log of the pool is kept. Resultsmust be recorded twice a day for public pools and once a day for semi-public pools. This isof great value as a source of information for the pool operator, as an assurance to responsibleofficials and the public that proper health and safety standards are being followed, and as areference for future operation of the pool facilities.2.3 PERSONNELSufficiently trained personnel should be available to accomplish effective pool management,bathhouse supervision, lifeguarding, and maintenance of filtration and re-circulation systems.We recommend that a permanent employee of the City or Park Board be assigned to maintainthe mechanical equipment.An adequate number of lifeguards are essential. Many authorities feel that at least onelifeguard should be provided for every 75 swimmers. Roving lifeguards, in addition to thoseon duty in the lifeguard chairs are desirable.The use of water safety aides to assist lifeguards in controlling patrons during periods ofheavy loading could markedly increase in efficiency. These aides are generally responsiblehigh school students who show an interest in pool activities. Pools operating on limitedbudgets may use aides and compensate the aides with free swimming. There is no substitutefor qualified lifeguards but, under certain circumstances, water safety aides may help preventa dangerous situation.The manager’s responsibility does not cease when the swimming period is over. Theswimming pool is an attractive nuisance and may be very dangerous if accessible when notofficially in use. Using the pool facilities without supervision must not be permitted.4

2.4 BATHHOUSEThe first contact the public has with the pool is the bathhouse and their opinion of the entirefacility will be based on what they see here. Good housekeeping is essential and results in aclean appearance that will greatly promote the swimming pool program. The bathhouseshould be adequately lighted and ventilated. Lavatories and toilets should be cleaned anddisinfected twice daily if odors and unsightliness are to be avoided. Adequate wastereceptacles should be provided.Clean floors are especially important. Contact with the dressing room floors, shower stalls,and other places where the fungus might live, frequently transmit athlete’s foot and otherfungal infections. In most pools, fungal infections may be controlled by a daily scrubbingwith hot, soapy water followed by liberal applications of a chlorine solution (1/4 to 1%).2.5 FOOTBATHSFootbaths for the control of athlete’s food have been known to promote the growth ofbacteria and shall be eliminated.2.6 SHOWERSAs a further aid in preventing the spread of disease, every effort should be made to inspect allpatrons and exclude those showing symptoms of infection. Before entering the pool, hotwater and soap shall be provided and nude bathing shall be required. This removes much ofthe perspiration, mucus, and bacteria from the swimmer’s body that otherwise would bewashed off in the pool. Some authorities state that permitting the public to swim withoutbathing reduces the efficiency of the disinfecting system by as much as 50%.It is important to remember at this point that good house keeping, along with a thoroughcleansing of the bather before entering the pool, will eliminate many of the operationaldifficulties that often develop.2.7 REGULATIONSThe following regulations should be enforced to assure the sanitation and purity of the pool.A. Refuse admission to all persons having any contagious disease or infectiouscondition such as a cold, ringworm, foot infections, etc. Also, exclude thosepersons with excessive sunburn, corn plasters, adhesive tape, or bandages ofany kind.B. Do not allow suntan ointments, food, gum, or tobacco in the pool area.C. Require nude showers before entering the pool.D. Glassware and similar material with a tendency to shatter on impact is notallowed in pool area.E. Unnecessary spouting of water, roughness, or rowdiness shall be prohibited inthe pool area.F. Domestic animals are not permitted in pool area.5

G. Diving is not permitted except in designated area.H. All diaper age children must wear waterproof diapers.2.8 POOL SAFETYAbout 80% of all accidents at the pool are the result of falls, which can be caused by walkdefects such as poor drainage, slippery surfaces, and steps. Pooling of water in low spots isthe most common reason for walk accidents. If the water stands and is not swept away, itwill collect dirt and algae, creating a slippery condition. This water is also a source ofbacterial contamination if carried into the swimming pool. It is good practice to scrub anddisinfect walkways in the same manner that is used for dressing rooms.Broken walks are a source of cuts and bruises. Cracks, broken sidewalks and walk areasshall be patched and properly pitched to drain away from the pool.A pool surface area of about 300 square feet around each diving board shall be restricted fordiving only, as injuries have occurred when divers have collided with each other. If thediving bay dimensions or water depth is limited, the heights of the diving boards shall berestricted to reduce the chances of injuries caused by divers colliding with the pool bottom orsides.Fatalities have occurred while swimming alone or when accidentally falling into a pool thatis either empty or inadequately supervised. Motel and private club pools are a special safetyhazard. Many of these pools do not have locked protective fences or barriers to controlaccess. These pools become attractive nuisances and are a hazard to both children andadults. Doors to all indoor pools should be kept locked when adequate supervision is notprovided. Fences or barriers shall protect outdoor pools.6

CHAPTER 3 - WATER CHEMISTRYA swimming pool, like a lake or stream, is subject to constant pollution, making it difficult tomaintain the water purity at all times. Wind blown dust and dirt, perspiration, mucus, andbacteria from swimmers’ bodies are all dissolved by the water, providing an ideal nutrient forthe growth of various microorganisms. These substances cause changes in the physical andchemical condition of the water, stimulating the growth of bacteria and algae. Lack ofvigilance on the part of the pool operator can cause massive bacterial and algal growths,resulting in high water turbidities and subsequent closing down of the swimming poolfacility.3.1 pHThere is a precise scientific definition for pH, of course, but for pool operators it is sufficientto state that pH is simply a numerical scale representing a condition of pool water. Itrepresents the degree to which water is acidic or basic. The scale ranges from 0 to 14, withthe midpoint, 7, representing the neutral condition – neither acidic nor basic. The scalemoves from this neutral condition at 7 upward to 14, representing an increasingly more basicor alkaline state. Below 7 the scale represents more acidity, with the lower numbersrepresenting a more strongly acidic condition. For example a pH of 4 is more acidic than apH of 6.The pH of pool water varies with mineral content and may require a chemicalanalysis to determine the optimum pH for stability to prevent scale orcorrosion from occurring. It is important that the pool water be kept on thealkaline side at all times. Therefore, a pH range of 7.2 to 7.8 is recommended.Neglect on the part of the pool operator to check and adjust the pH will createoperational problems should the pH fall outside the recommended limits.Some problems that may occur with an improper pH are:(a) Irritation to eye and mucous membranes of the bathers.(b) Unstable chlorine residuals.(c) Corrosion or scaling problems.(d) Turbidity problems caused by chemical imbalance.Body acids introduced by bathers and the addition of gas chlorine are the majorreasons for the pH to drop. The pH will rise with the addition of calcium,hypochlorite, sodium hypochlorite, and soda ash. Since chlorine and bathers are anormal part of the operation of swimming pools, it can be seen that adjustment of thepH must be done daily.3.2 ADJUSTING pHAdding soda ash (sodium carbonate) normally does raise the pH. Soda ash is available as apowder in 100-lb bags. When added to water, soda ash combines with carbon dioxideproducing sodium bicarbonate, the desired type of alkalinity.7

Soda ash should be applied with a solution pump capable of feeding accurate amounts ofsoda ash solution. About 1.2 lbs. of soda ash is necessary for each pound of chlorine gas tomaintain a constant pH and to prevent the water from becoming corrosive. It is falseeconomy to shorten the life of the equipment by the small savings realized from insufficientuse of soda ash.Adding muriatic acid (a commercial name for hydrochloric acid) normally does lower thepH, which often must be done when calcium hypochlorite or sodium hypochlorite is used asthe disinfectant. The pH may also be lowered using a dilute from of sulfuric acid (40%strength) or sodium bisulfate. Sodium bisulfate is a dry form of acid, milder than the liquidtypes and much safer to handle, but more expensive.Severe damage has occurred to pool equipment when operators have added the acid withoutfirst diluting it. Dilute the acid at least 2 to 1 before adding it to the pool. To preventsplattering, always add the acid to the water. NEVER ADD WATER TO ACID.3.3 ALKALINITYPool operators are seldom aware of alkalinity or, more specifically, bicarbonate alkalinity.Few test kits sold to operators are equipped for checking alkalinity, yet a pool with noalkalinity would be completely unmanageable, as the pH would rapidly fluctuate.Maintaining the proper alkalinity will provide a buffer against rapid pH changes that couldoccur with changes in bather loads or chemical feed rates.The recommended alkalinity of a swimming pool is between 100 and 150 mg/l. For poolsusing hypochlorite solutions, the alkalinity should be maintained slightly lower, at about 70to 80 mg/l, as the hypochlorite solutions add alkalinity.3.4 ADJUSTING ALKALINITYSome pool operators have difficulty in maintaining the pH low enough even though theydiscontinue the use of soda ash. These pools usually have make-up water of high alkalinityand/or may use hypochlorite solutions which add to the alkalinity of the water. Feedingmuriatic acid or a solution of sodium bisulfate may control excessive alkalinity.Waters of excessive alkalinity and high pH, common in western North Dakota, mayprecipitate dissolved minerals such as calcium, magnesium, iron, and manganese, resulting inconsiderable pool turbidity. Such waters require the addition of large quantities of acid forstabilization. The addition of 1.5 pints of muriatic acid per 10,000 gallons of water willlower the total alkalinity by 10 mg/l. The acid will lower the pH to the recommended level,but may not be in an amount sufficient to neutralize the excessive alkalinity. When thiscondition occurs, the pH may rise to near the original level in a relatively short time.Additional acid must be added at intervals until the pH finally stabilizes within the desiredrange.8

Pools with low alkalinity may be adjusted upwards with the addition of sodium bicarbonate.The addition of 1.5 lbs. of sodium bicarbonate per 10,000 gallons of water will raise the totalalkalinity by 10 mg/l. If the pH needs adjustment upward, then soda ash may be used toincrease both the alkalinity and the pH.3.5 HARDNESSHardness in swimming pools consists mainly of the dissolved salts of calcium andmagnesium. Hardness is generally not a problem when the total alkalinity and pH are keptwithin limits. Therefore, testing for hardness and adjusting the level are not necessary afterthe initial filling of the pool. Very soft waters may be turbid and may have to be adjusted toat least 150 ppm total hardness to obtain clarity.3.6 ADJUSTING HARDNESSThe total hardness may be increased without an increase in alkalinity by adding calciumchloride. A dosage of 0.2 lbs. of calcium chloride in 25,000 gallons of water will increasethe hardness by 1 ppm. Additional calcium chloride may have to be added from time to timedepending upon the amount of make-up water added. Use this procedure only with waters oflow hardness and high alkalinity because it can increase the corrosive tendency of the water.9

CHAPTER 4 - DISINFECTIONSwimming pools receive all manners of dirt and debris and it is essential that some form ofdisinfectant be used to destroy any potentially dangerous organisms. To do this, swimmingpool disinfectants must possess certain properties. Above all others, they must be effectiveand must be capable of rapidly killing bacteria. They must have residual properties such thatthey maintain a presence in the water to eliminate bacteria and harmful organisms as theyenter the pool. A disinfectant must be safe and harmless to bathers. It should not createundesirable conditions in the pool. It must be readily available, inexpensive, easily storedand handled, and it should possess algaecidal properties.4.1 CHLORINEThe most common means of swimming pool disinfection is through the application ofchlorine. Chlorinating of pool water will provide for disinfection to kill bacteria and diseaseproducingmicroorganisms, which might infect bathers and oxidation (to react with anddestroy other contaminants such as algae, body oil, minerals, dust, and other materials, whichcause color, odor, and turbidity). The advantages of using chlorine as a swimming pooldisinfectant are:A. Chlorine is effective. It possesses both bactericidal and algaecidal properties.B. It is easy to store and handle.C. It is available in a variety of forms such as a gas, liquid, or solid.D. It can be dispensed by hand or automatically through a wide variety ofdevices.E. Its presence in water is easily detected and measured.F. It is widely available and relatively inexpensive.When chlorine, in any form, is added to water a chemical reaction takes place with theresulting formation of hypochlorous acid. This is the chemical agent which reacts with anddestroys bacteria and other undesirable contaminants in pool water. The amount ofhypochlorous acid, which is produced by this reaction, is dependent on the pH of the water.Therefore, maintaining the pH within the proper range will also aid in establishing andmaintaining an adequate and effective chlorine residual.Chlorine is a very active chemical. As it is added to the water, it will react with manysubstances both dissolved and suspended in the water in the following ways: (pg 13, fig 1).10

A. CHLORINE DEMAND: Swimming pools are reservoirs open to contamination forall manners of dirt and debris. Bathers, rain, wind, and chemicals can also contributeimpurities to the water. When chlorine is added to a pool, it immediately reacts withand begins to destroy some of this foreign matter. The amount of chlorine required toreact completely with these chlorine-destroying compounds is termed the “chlorinedemand”. Also related to chlorine demand is the amount of chlorine required to killthe bacteria and other microorganisms present in the water. Sufficient chlorine mustbe added to the pool water to satisfy its chlorine demand, in addition to the amountrequired to maintain an adequate residual.B. COMBINED CHLORINE RESIDUAL: As more chlorine is added to the water, itwill react with any dissolved ammonia present to produce combined chlorine(chloramines). These products are odorous, irritating to the eyes and mucousmembranes and are weak disinfectants.C. BREAKPOINT: Further addition of chlorine will oxidize the previously formedchloramines and cause the combined chlorine residual to be reduced to almost zero.As reaction of all chloramines nears completion, additional chlorine will be retainedin the water as a residual and will be available to act on bacteria, which may besubsequently introduced into the pool water. This point on the curve is referred to asthe break point.D. FREE CHLORINE RESIDUAL: Residual chlorine exists after break point as freechlorine (hypochlorous acid), which is a strong disinfectant. This is the desired areaon the curve due to the nearly complete oxidation of all bacteria and contaminantsand the presence of a strong disinfectant in the form of free chlorine. To insure thatadequate disinfecting is taking place, it is a requirement under Fargo Municipal Code13-10 that a minimum free chlorine residual of 1.0 ppm be maintained at all times.Various ammonia and nitrogen products may enter the pool through wind blown plantlife and perspiration and urine from bathers. Their levels can gradually build up until11

a substantial amount of chloramines are being formed due to the reaction with thechlorine residual. This will cause the free chlorine residual to drop, therebydecreasing disinfection effectiveness, causing irritations to the eyes and mucousmembranes, and producing associated odors. This undesirable condition can beavoided to a great degree by routinely super-chlorinating. Super-chlorination is theprocess of quickly raising the free chlorine residual 5.0 to 10.0 ppm and then allowingthis higher residual to dissipate over night. Super-chlorination can be performed onan established schedule, for example, every two weeks or a test kit can be used todetermine when it is necessary. If testing of the pool water shows an appreciableamount of combined chlorine (the difference between the total and free residuals), 0.2ppm or more, then super-chlorination may be necessary. This method will be moreeconomical and accurate than an established schedule, but either will work.Chlorination, as the term implies, is the practice of introducing chlorine to pool water.Regardless of the product used or the method of application, the goal is to achieve achlorine residual possessing strong oxidizing and disinfecting properties. Chlorinemay be supplied as a gas, a solid, or a liquid, each having different handling andsafety conditions, but still providing chlorine for effective disinfection.4.2 CHLORINE GASChlorine gas is packaged under pressure as a liquid in metal cylinders and is fed into thesystem by a chlorinator, which regulates the amount of gas which; is introduced. Thecylinders are of seamless steel construction with an operating valve equipped with a safetydevice in the form of a fusible metal plug. These plugs are designed to melt at 158ºF topermit the escape of chlorine gas to prevent tank rupture. This fusible plug should not betampered with under any circumstances.The valve on the chlorine cylinder has a non-standard pipe thread requiring a special wrench.The use of these non-standard connections is intended to discourage anyone from usingpliers, wrenches, or hammers to force connections or otherwise depart from standardhandling techniques. If you do not presently have one of these special wrenches, pleaseobtain one from your chlorine supplier. The wrench must remain on the valves in use at alltimes.Always use a new lead washer when connecting a chlorine cylinder to the chlorinator. Openthe valve only one-quarter to one-half turn after connecting the chlorinator and check theconnection for the presence of leads. This may be accomplished by holding a swabmoistened in ammonia near all the connections. The presence of chlorine gas will beindicated by the formation of a white smoke-like cloud of ammonium chloride. Do not forcethe chlorine cylinder valve if it is difficult to open. Damage to the valve may occur, causinga major chlorine leak. Return the cylinder to the supplier rather than risk the danger of a leakcaused by a broken valve.The quantity of gas in a chlorine cylinder can be determined only by weighing the cylinderon a platform scale. When a new cylinder is connected to the chlorinator, its weight should12

e noted. Daily loss of weight records will indicate the number of pounds of chlorine usedduring the previous day and will indicate when the cylinder is empty.Before removing the chlorine cylinder from the chlorinator, be sure the valve is closed andtested for leaks. Replace the valve hood. The empty tank should then be treated and handledas though full until it is removed from the premises.If a leak occurs, all persons should be cleared from the area and kept away until the cause ofthe leak is found and the trouble corrected. Any person overcome by, or exposed to chlorineshould be moved at once to an uncontaminated area and should be kept completely at restand warm until medical assistance can be obtained. If breathing has ceased, immediatelyapply artificial respiration or use approved inhalation equipment or oxygen.4.3 CALCIUM HYPOCHLORITEChlorine is also available as a granular powder or in solid tablets. The most common form ofdry chlorine is calcium hypochlorite, which contains 65% available chlorine. Calciumhypochlorite is commonly used as a disinfecting agent for pool water, decks, dressing rooms,and equipment. It is safer material than chlorine gas with respect to handling and feeding,but it may present serious problems if spilled or scattered in a moist or wet environment or ifoxidizable material is introduced to the container.Calcium hypochlorite can be manually fed directly into the pool from handheld containers toeither facilitate super chlorination or as an alternative feed in the event of equipment failure.Normally, however, it is mixed with water in tanks and the clear liquid is fed to the recirculationsystem by means of mechanical feeders or hypo chlorinator. A heavy precipitateof calcium carbonate forms when calcium hypochlorite is dissolved in water, so this must beallowed to settle and the clear liquid siphoned off the top. When calcium hypochlorite isused as a source of chlorine for public swimming pools, it is recommended that the chemicalbe fed continuously by means of a chemical feeder.Calcium hypochlorite is often used for chlorination of small private and semi-publicswimming pools. Several methods may be used for applying this chemical.A. Granular calcium hypochlorite can be broadcast over the surface of the poolwater.B. A solution of calcium hypochlorite can be poured on top of the water.C. A stock solution may be fed continuously by means of a diaphragm typeproportioningpump.Calcium hypochlorite is a powerful oxidizing agent and the hazards attributed to this productare directly related to its oxidizing power. Calcium hypochlorite may be used with safety ifthe following precautions are followed:A. Always keep calcium hypochlorite in its original container and store in a cool,dry place away from oils, rags, and other combustible organic materials.B. Use only a clean, dry, non-combustible scoop when handling the powder.C. Never mix calcium hypochlorite with other chemicals.13

D. Always pour calcium hypochlorite into the water when making a solution.E. Wash hands immediately after handling.F. Clean up any spilled material immediately by flushing down a drain.G. Avoid inhaling the calcium hypochlorite dust.H. Read and follow directions on the label of the container.4.4 SODIUM HYPOCHLORITESodium hypochlorite is a liquid compound (5.25 to 6% available chlorine) sold as ahousehold bleach. In a commercial form it may be obtained in strengths up to 10% availablechlorine and is usually purchased in one gallon jugs, five gallon carboys, or 55 gallon drums.4.5 STABILIZERCyanuric acid, or simply stabilizer, is a chlorine-extending compound. It reportedly helpschlorine resist the deteriorating effects of ultraviolet light (sunlight). One serious drawback inusing chlorine has been its susceptibility to the weakening effects of sunlight, especially inoutdoor pools. Cyanuric acid acts as a shield, protecting the free chlorine residual from theseeffects and extending its useful life.Cyanuric acid stabilizer is a semi-permanent additive. Losses from the pool usually occurfrom splash out and drag out into the deck area, filter backwash, vacuuming to waste andleakage. In other words, when water is physically removed from the pool, the stabilizer goeswith it. Assuming that the pool does not leak, stabilizer losses will be very small on a day today basis.One serious drawback to the use of cyanuric acid is that it reduces the effectiveness of thechlorine residual. A stabilized free chlorine residual is only about 40% as effective as anequivalent value of free chlorine with no cyanuric acid present. This means that to obtainequivalent disinfecting action, the stabilized free chlorine residual would have to be two andone half times greater (at least 2.5 ppm) than a free chlorine residual without cyanuric acidstabilization.Some chlorine compounds already contain cyanuric acid and are known as chlorinatedisocynaurates, cyanurates, or stabilized chlorine. They contain 60% available chlorine andare designed to do two jobs at once. While killing bacteria and algae, they also add ameasured quantity of stabilizer sufficient to maintain an effective level. The danger of usingthese chemicals as the only disinfecting agent is the gradual buildup of cyanuric acid (whichis toxic at high concentrations) in the pool water over an extended time. Whey the cyanuricacid level exceeds the maximum value; it may be reduced only by diluting the pool waterwith water that is free of cyanuric acid.It is certainly not necessary to use the chlorinated isocynaurates to stabilize the pool.Stabilizer may be purchased as cyanuric acid, a whit granular powder. At the time of poolstart up, it may be added slowly through the skimmer and in sufficient quantity to achieve a14

esidual of between 30 and 100 ppm. Consider 40 ppm as the ideal level. Follow thedirections on the package for adding the recommended quantity to reach the ideal level.4.6 BROMINEA dry bromine compound containing about 66% bromine is normally used for swimmingpools. It has reduced the danger involved in handling bromine chemicals to a risk similar tothat experienced with dry chlorine. Bromine is more expensive than chlorine and itsbactericidal effectiveness is slightly less. The bromines primary advantage is that it is lessaffected by pH than chlorine. When combined with organic materials, perspiration, urine,etc., the compounds which form the bromamines have disinfecting capabilities similar to freebromine. These compounds are also less irritating to the eyes and mucous membranes thanare chloramines.One further advantage of bromine is that it remains fairly stable in pool water as thetemperature rises. Since spas and hot tubs maintain water temperatures higher than thosenormally found in swimming pools, bromine could be used in these cases.A disadvantage of using bromine is that the pH must be maintained in a range of 7.0 to 7.4,which increases corrosion problems.Bromine levels should be kept between 1.0 and 3.0 ppm. A chlorine test kit may be used tomeasure these values, but the reading obtained must be multiplied by 2.25 to obtain theactual bromine level in the water.4.7 OZONEOzone has proven itself over the years as a powerful disinfectant and oxidizer in treatingdrinking water. It is expensive to generate, toxic, corrosive, and does not leave a disinfectingresidual. For these reasons, ozone is not a suitable disinfectant for pool use. Should ozonebe used, another disinfectant such as chlorine, maintained at a proper level, must be used toprovide a constant disinfecting residual.Ozone equipment should be located in a separate room. Even minor leaks could severelydamage the pool equipment, as ozone is extremely corrosive. Careful monitoring of theozone levels must be made to insure that ozone is not present in the pool area especially inindoor pools, as ozone is also toxic.4.8 ULTRAVIOLETUltraviolet radiation has been used to disinfect water supplies but, like ozone, does not leavea disinfecting residual. Also, the water must be completely free of turbidity becauseultraviolet radiation has limited powers of penetration into water. Should ultravioletradiation be used, chlorine or another disinfectant maintained at the proper level, must beused to provide a constant disinfecting residual.15

4.9 IODINEIodine is an effective bactericide for swimming pool use. Iodine residuals have normallybeen obtained through the chemical reaction of an iodine compound such as potassium iodideand chlorine. Iodine produces a long lasting residual, making it a good choice for decks anddressing rooms. The use of iodine produces a characteristic iodine odor in the pool area andcauses the water to take on a yellow-green color (for aesthetic purposes, a high level of pH isdesired to prevent water discoloration). Iodine has been more expensive to use as comparedto chlorine. This, coupled with the odor and color problems, has all but eliminated the use ofiodine in swimming pools. Iodine levels may be measured with a chlorine test kit bymultiplying the reading by 3.6.16

CHAPTER 5 - RECIRCULATIONA re-circulating type of pool has the necessary equipment to keep the water continuouslyclean and disinfected. Water is drawn from the pool through a hair and lint strainer by meansof a centrifugal pump and then to the filters for removal of fine suspended material. Afterfiltration, the finished water is returned to the pool through the inlets. This round trip thewater takes is called the “turnover rate”. The capacity of the re-circulation system must besufficient to provide one complete turnover of the pool water every six hours (1-hour forwading pools and 30 min for spa type pools).All of the water, however, does not go through the filters every six hours. The water that isfiltered comes back to and mixes with the water in the pool and a portion of this water goesback through the filters. Continuous (24 hour per day) re-circulation reduces the amount ofwater that does not pass through the filters. Studies have indicated that a six-hour turnoverrate will provide 95% to 98 % dilution of the pool water with filtered and chlorinated water.There will always be some water that does not get filtered and chlorinated, resulting in thesurvival of algae, bacteria and other organisms.5.1 HAIR AND LINT STRAINERThe hair and lint strainer located on the suction side of the pump is necessary to protect thepump impellers from damage or clogging by foreign material such as stones, leaves, lint, andhair. The strainer should be cleaned as often as necessary, but not less than once weekly, toprevent the loss of the pumps efficiency by the buildup of debris. Severe accumulation in thestrainer will prevent sufficient flow of water to the pump and could cause “cavitation”, whichwill result in noise, vibration and erratic performance of the pump. Prolonged cavitation willresult in serious damage to the pump impeller, bearings, and seal. Two strainers should beprovided so that a clean one is available for immediate replacement. The wing nuts on thestrainer bowl cover should also be firmly tightened to prevent air leaks.5.2 PUMPSThe heart of the re-circulation system is pump. It draws water from the pool, forces itthrough the filter and returns it to the pool. Single stage centrifugal pumps are commonlyused due to their low cost and maintenance. The pump, and particularly the motor, should beprotected against excessive moisture and chemicals. The floor of the pump room should beequipped with a drain and adequate ventilation should be provided at all times.The packing glands of centrifugal pumps are lubricated by a controlled leakage of water.The stuffing box gland nut should be adjusted to provide a leakage rate of several drops perminute.Most pool pumps are self-priming, but they should never be run dry. Even a short run on dryseals will injure them. Self-priming is accomplished by removing the cover from the pumpstrainer bowl and filling it with water. The pump will not self-prime unless the strainer bowlhas water in it.17

Centrifugal pumps, which are not self-priming, are primed by allowing the air on the suctionside to escape through a bleeding valve or plug on the top of the pump casing. This allowsthe pump and impellers to be flooded on the suction side. Priming must be done with thepump not running to prevent damage to the water-lubricated packing rings.Lubrication of the ball bearings on the pump and motor should be done as prescribed in themanufacturer’s instructions. Lime soap grease is often used as the lubricant. Care should betaken to prevent over lubrication, as this can result in heat damage to the bearing surfaces.Some of the more common operational difficulties encountered with pumps are:A. Failure to pump: This may be due to lack of priming, wrong direction ofimpeller rotation, or insufficient motor speed.B. Reduced pumping capacity: Probable causes are air leaks in the suction line,clogged hair and lint strainer, or closed valves.C. Mechanical trouble and noise: This may be caused by misalignment of themotor pump shaft, a bent shaft, damaged bearings, or improperly proportionedsuction and discharge lines.D. Excessive leakage of water: The packing glands may need to be tightened ornew packing rings installed.Any unusual operational problems with the motor should be noted and a qualifiedserviceman called for servicing.5.3 SAND FILTERSBoth gravity and pressure type sand filters are in use in North Dakota. For proper operation,sand filters should be equipped with a rate-of-flow indicator and loss-of-head gauges.Pressure filters should also be equipped with an air relief valve to prevent the filter frombecoming air-bound. This valve should be opened at least daily to remove the air thatcollects in the top of the filter area. Care should be taken to see that automatic-type air reliefvalves are not sealed during the annual painting period.Its surface area determines the capacity of a sand filter. Sand filters are designed to operateat a filtration rate of from 2 to 3 gallons per minute per square foot of surface area.As the filter is used, an increase in loss-of-head or resistance to flow of water is noted. Thefreshly washed sand filter has some initial loss of head, usually about 2 feet, equal to apressure of about one pound per square inch (psi). Gravity filters should be washed when theloss-of-head reaches from 7 to 9 feet. Pressure filters are generally back-washed when theloss-of-head reaches 5 to 7 psi.Cleaning of sand filters is accomplished by reversing the water flow and pumping it throughthe filter at a rate of 15 gallons per minute per square foot of filter area. This backwashshould usually continue for 5 to 10 minutes.18

An insufficient backwash rate will not thoroughly clean the sand bed and serious filtertroubles may result. Cleaner filters and a saving on wash water may sometimes be obtainedby breaking up or agitating the top of the sand layer before washing.After cleaning, a small amount of aluminum sulfate (alum) is usually added to the top of thefilter bed for coagulation purposes. The alum reacts with the alkalinity in the water,producing aluminum hydroxide. Aluminum hydroxide is a sticky gelatinous substance,which clings to the sand particles and strains out the fine suspensions in the water. Careshould be taken not to add too much alum, as an excess may add turbidity to the water. Inmost cases, 2 oz. of alum per square foot of filter surface is adequate.Use only potassium alum for coagulation and not the so-called ammonia alum. Theammonia alum introduces large amounts of ammonia into the pool water. This ammoniacombines with the chlorine present forming chloramines, greatly increasing the chlorinedemand of the water.Some common problems associated with sand filters are:A. Plugging. Routine inspections of the filter bed should be made to see that thesand is free from dirt and channels. Slowly wash the filter with the cover offand check to see if the water leaks through the sand surface evenly. Unevenup-flow of the water indicates that the under-drain nozzles are clogged or thatthere are obstructions in the sand bed. Removal of the filter sand would benecessary to replace the nozzles. Occasionally, treatment with a strongsolution of sodium bisulfate is effective to prevent clogging. Two pounds ofsodium bisulfate are added per square foot of filter area. Allow the sand tosoak about 12 hours and then backwash. Acid treatment of this type maycause some corrosion damage.In areas with hard water, care must be taken to prevent the precipitatingcalcium and magnesium salts in the water from causing scale buildup on thesand and under-drains, resulting in clogging that cannot be removed by backwashing.Chemical cleaning will be required in these cases. The use of watersofteners for treating the pool water would be highly beneficial in these areas.B. Mud Balls. Mud balls consist of large accumulations of dirt and sand heldtogether by organic growths. These organic growths may consist of filteredalgae, bacterial organisms, or surface debris removed by the filters. Mud ballsusually occur because of insufficient wash rate and the lack of chlorine in thefilter influent. Maintaining clean filters may prevent mud balls. Provide asufficient backwash rate of at least 15 gallons per minute per square foot ofsurface area. Chlorine should be fed ahead of the filters so that the sand iscovered with a strong chlorine residual at all times. This will prevent bacterialand algae growths from forming on the filter surface.C. Oil and Grease. Frequently, the sand particles become coated with oils andgrease as well as with an accumulation of hair and dirt. Detergents areeffective in removing oil and grease from sand filters. Add a solution(approximately 1 pound of sodium hexametaphosphate per 100 gallons of19

water) to the filter in an amount sufficient to cover the sand. Soak the sandseveral hours, re-circulating through the make-up water tank when possible.Drain to waste and thoroughly backwash.The filter piping should have a re-circulation line to permit re-circulation of the water fromthe effluent back to the influent for chemical cleaning of the filter media. This line should beabout one-half the size of the main return piping.Sand contaminated with oil and grease had been traditionally cleaned with a lye solution.This procedure should only be used if other materials are not effective. Lower the waterlevel in the filter to within 2 inches of the top of the sand and apply the lye at a rate of 1pound per square foot of the sand surface. Allow the upper portion of the sand to soakseveral hours and slowly empty the filter to waste. Follow with a longer than usualbackwash. This treatment will prevent replacement of costly filter sand. Provide adequatewash water flow rates to prevent further accumulation of such conditions. Use extremecaution when handling lye as it can cause severe burns. Lye is particularly destructive to thetissue of the eye and may cause loss of sight.5.4 HIGH RATE SAND FILTERSHigh rate sand filters may be operated at filter flow rates of up to 10 gallons per minute persquare foot of surface area (as compared to 2 to 3 for conventional sand filters). Filtration isaccomplished in-depth rather than on the surface, thereby, increasing the dirt holdingcapacity of the filter.Operation and cleaning of high rate sand filters should be compliant with the instructionssupplied by the manufacturer. Usually the filter is back-washed when the differentialpressure reaches 25 psi. The design of the under drain system causes strong agitation,rubbing together the sand grains to release suspended materials. Trade literature indicatesthat the collected solids are generally discharged during the first minute or less of backwashwater source within about 2 minutes. Recommended backwash periods vary, but for somefilters it is approximately 2 ½ minutes.High rate sand filters have had erratic success in North Dakota. Operation of the filter at aconsiderably reduced flow rate after back washing may prove beneficial. The reduced flowwill allow the suspended materials to collect and settle on the sand, rather than being drivencompletely through the clean filter media. Once a coating of suspended material has beenbuilt up on the filter surface, the flow may be increased to the normal re-circulation rate.5.5 DIATOMACEOUS EARTH FILTERSThis type of filter has several advantages over the sand filter; greater removal of turbidity,smaller size and the elimination of chemical coagulants such as alum. They also require verylittle water for back washing.20

Diatomaceous earth is the skeletal remains of a type of microscopic plant called diatoms,which flourished in lakes in early geological times. There they decomposed, leaving onlytheir white, silica-impregnated porous skeletons, which settled to the lake bottom formingdeposits of diatomaceous earth.Basically, the operation of diatomaceous earth (D.E.) filters consists of pre-coating a numberof porous filter elements with a slurry or solution of diatomaceous earth. The key to thesystem is the filter element, the most common of which is the septum; a cloth covered plasticgrid. The cloth of the septum is initially coated with diatomaceous earth by the re-circulatingthe water from the effluent of the filter to influent through a bypass line while the D.E. feederis operating. This results in the cloth surface of the filter elements becoming coated withD.E. material. It is this “cake” of diatomaceous earth, which performs the filter action,trapping dirt on the porous D.E. while allowing the water to pass through. Once the elementshave become coated, the filter can be placed into normal operation.Most filter manufacturers recommend pre-coating at a rate of 1.0 to 1.5 pounds of filter aidmaterial per 10 square feet of filter surface area. Additional amounts of the diatomaceousearth slurry are added continuously during the filtering cycle to prevent packing of thefiltered material. The amount of slurry to be added varies with water quality, type of filter,and other conditions. As the cycle continues, the filter cake gradually builds up a resistanceto the water flow and if not carefully controlled, can reduce the efficiency of the unit.Pressure diatomaceous earth filters are back-washed when the loss-of-head reaches up to 20to 25 psi. Recommended head loss pressures vary with the filter manufacturer and may beconsiderably less for some installations. Always follow the backwash procedurerecommended by the manufacturer. Backwash consists of reversing the water flow andincreasing the water velocity up to 5 to 10 gallons per minute per square foot. Strong surgesof wash water are effective for cleaning the filter elements.Vacuum type diatomaceous filters are back-washed when the pressure loss through the filterreaches a predetermined level on a vacuum gauge. Again, the manufacturer’s operationalrecommendation should be followed. Some manufacturers recommend back washing whenthe vacuum gauge reads approximately 15 inches of mercury or about 7.5 psi. In washing,the filter aid adhering to the septum is gently broken up with water from a hose, the drainvalve is opened, and the filter cake is flushed to the drain pump.Diatomite filters should be chemically cleaned when excessive head losses are noted,immediately after pre-coating. Chemical treatment should be accomplished with a closed recirculationsystem. No damage to the re-circulation system should result when the filterelements are of synthetic or metallic material.The filter elements may be cleaned while in the filter or removed and cleaned manually.Manual cleaning is generally more effective.The amount of chemicals used for cleaning the elements, without removal from the tank, willdepend upon the degree of clogging. The filter is back-washed, filled with water, isolatedfrom the pool, and re-circulated. The necessary chemicals to be used for treatment are added21

and re-circulated through the filter tank for one to two hours. The filter is then drained,flushed, pre-coated, and placed back in operation.To remove build-up of common materials, the following methods may be applied:A. Iron. Add approximately 1 lb. of crystalline oxalic acid to each 125 gal. ofwater in the filter.B. Manganese. Same as for iron, with the addition of about 1 oz. of sodiumbisulfate for each 100 gallons of the acid solution in the filter. Add thebisulfate slowly over a period of time to prevent the formation of sulfurdioxide gas.C. Oil and Grease. Add about 1 lb. of sodium hexametaphosphate (a commercialcompound is “Calgon”) per 100 gallons of water in the filter.D. Diatomite Clogging. Same as for oil and grease.E. Organic Matter. Same as for oil and grease. An alternative of 10 ppm ofchlorine solution is sometimes effective.F. Calcium and Magnesium. Add about 1 gal. of muriatic acid per 125 gallonsof water in the filter.When cleaning the elements in the filter is not effective; removal of the elements and manualcleaning may be required. Manual cleaning of common materials from the filter elementsmay be accomplished using the following solutions:A. Iron, Calcium, and Magnesium. Dilute muriatic acid.B. Manganese. Same as for iron, with the addition of a small amount of sodiumbisulfate.C. Oil, Grease, Organic Matter, and Diatomite. An 8% solution of sodiumhexametaphosphate.Use extreme caution when handling acids, as they are harmful to the eyes, skin, and clothing.Oxalic acid is poisonous when taken internally.Washing them with a detergent in an ordinary washing machine may clean the plastic fabricand drop sleeves.5.6 CARTRIDGE FILTERSCartridge type filters have several advantages over the sand and diatomaceous earth filters.Among the advantages are much lower initial cost of installation, longer filter runs, compactsize, and replaceable filter elements. In addition, no water is wasted for back washing.Operational costs for cartridge filters are higher than for any other type of filter, however, asthe filter elements have a life expectancy of them from a few months to a few year.Cartridge filters consist of filter elements made of paper, cloth or a combination of both.Individual filter elements are normally about 12 inches in length and a few inches indiameter, but contain about 4 to 6 sq. feet of filter area. Even though cartridge filters aredesigned to operate at flows of 0.375 gallons per minute or less, the large surface areacontained in one filter element enables the size of a filter unit to remain relatively compact.22

Cartridge cleaning is necessary only when the flow falls below that required or whenpressure increases or start-up pressure exceeds 10 to 15 psi. Operation and cleaning ofcartridge filters should be in compliance with the instructions supplied by the manufacturer.It should be noted that cleaning the cartridge elements is a time consuming chore. It isrecommended that two sets of cartridge elements be used to permit continuous operation ofthe filter unit while one set is out for cleaning.It has been found that the best performance and maximum length of time between backwashing can be achieved if the following procedures are used each time during cleaning:A. In most cases, using a pressure nozzle on the end of a garden hose can cleanthe cartridges. By directing the spray at the elements on an angle, most of thedirt may be removed.B. Sun tan oils may coat the cartridges and cause reduced flow. This materialmay be removed by soaking the cartridges in a mild solution of trisodiumphosphate and water. Usually 60 minutes soaking time will break the oilcoating from the elements. Trisodium phosphate is available at mosthardware stores or janitorial supply houses.C. Algae may also be removed from cartridge elements by soaking as long asnecessary in a strong solution of trisodium phosphate. Cartridges pluggedwith clay or vegetation may be cleaned using the same method.D. Calcium deposits may also be present on the filter elements. If calciumhypochlorite is used for disinfecting purposes in the pool, the calcium buildupmay be excessive. The cartridges should first be soaked in trisodiumphosphate for removal of other materials and then rinsed. They should thenbe soaked in a solution of 1 part muriatic acid to 20 parts water until thebubbling action stops. Always use a plastic garbage container or similarvessel to soak the cartridges in.5.7 LENGTH OF OPERATIONSand, diatomaceous earth, and cartridge filters should be operated continuously (24 hours perday) to maintain a clear pool water. A common mistake of many pool operators is to reducefiltration on cloudy days or during periods of light bather loading. Take advantage of thesetimes to allow the filters and chlorination system to remove the buildup of organic material inthe water.23

6.1 SWIMMING POOL START UPCHAPTER 6 - SPECIAL CONDITIONSProper pre-conditioning of the swimming pool water after initial filling is essential forsuccessful seasonal operation. Most authorities recommend that the pool be filled directlyfrom the filler spout and not through the filter system. Many North Dakota waters containlarge amounts of iron, manganese, and color, which must be removed prior to operation.After the pool is filled, the water should be superchlorinated with a chlorine dosage ofapproximately 10 ppm. This will disinfect the water, satisfy the chlorine demand, andprecipitate the iron and manganese. These precipitated materials can then be removed fromthe pool bottom by vacuum cleaning prior to start-up of the filtration equipment.When the color or iron is not removed by the high initial chlorine dosage, coagulation withalum may be necessary.6.2 POOL TEMPERATUREThe ideal water temperature for pools is a range of 76°F to 78°F. Temperatures over 80°Fmay lead to bathers’ discomfort and increase algae and bacterial growth. Swimming shouldnot be permitted if the water temperature drops below 65°F.Heating the pool water is desirable for swimming during cool weather. The pool heatershould be thermostatically operated to prevent the pool water temperature from droppingbelow 65°F. This will permit raising pool temperatures to a comfortable swimmingtemperature in a shorter time. Problems commonly encountered in all water heaters are:A. Rapid scale formation on the heating surface.B. Severe corrosion on the waterside of the heating surface.C. Condensation forming on the fire side of the heating surfaces results indeterioration of the boiler surfaces.Softening of the pool water with zeolite type water softeners and/or the use of stabilizingagents such as polyphosphates may prove helpful. Care, however, should be taken that thepH of the water is adequately controlled so that a corrosive condition does not develop.6.3 WIND PROTECTIONThe use of windscreens or fences adds considerably to bather comfort during periods ofinclement weather. Windscreens reduce the wind action and trap the solar heat, extendingthe time available for swimming activities.Wind screens built of wood or fiberglass is effective, but reduces the spectator area. Portablescreens of canvas or plastic are popular. These materials, when equipped with grommets,may be fastened to the barrier fence as needed.24

6.4 POOL BOTTOMThe pool bottom should be kept free of visible sediment and dirt at all times. Two methodsof cleaning in common use are brushes having long handles and suction cleaners. Brusheshave the advantages of low cost and ease of use on small pools. In many cases, however, thecombination of brushing and vacuum cleaning has worked the best.Hairpins or other metal objects should not be allowed to remain on the pool bottom, as theywill cause stains. A daily inspection should be made for these metal objects. They may beremoved by hand, by brushing, or by the use of a magnet attached to a long pole.6.5 SURFACE FILMThe pool surface should be kept free of floating film and debris. A hand skimmer should beavailable, consisting of a fine mesh net on an extension handle. Floating materials such asleaves or visible dirt should be skimmed routinely with this netting.In those pools having an overflow gutter system discharging to waste, fresh water should beadded at least once daily to the pool so that skimming action will take place for 10 to 15minutes. This will eliminate much of the floating materials. Pools equipped with surfaceskimmers or overflow collection systems will have constant skimming action with recirculationthrough the filtration system.6.6 HARD WATER SCALEWhen the swimming pool contains a hard, mineralized water, incrustation of the pumps,piping, heaters, and other appurtenances develop. This incrustation is composed primarily ofcompounds of calcium and magnesium. This precipitated material adheres to metal parts,forming a hard scale of calcium and/or magnesium carbonate.One way of removing the undesirable calcium and magnesium is to run the pool waterthrough a zeolite-type water softener. This has proved successful at many pools for treatingthe water used for filling the pool as well as the make up water. In addition, the zeolitesoftener may remove small amounts of iron in the solution.Sequestering agents such as sodium hexametaphosphate may prove beneficial. Thesepolyphosphate compounds tend to keep the calcium and magnesium carbonates insuspension, thus reducing their scale-forming action on metal surfaces. Some authoritiesrecommend an initial dosage of about 2 oz. by weight of sodium hexametaphosphate to each1,000 gallons of pool water, followed by a weekly addition of approximately 0.5 to 0.75 oz.per 1,000 gallons of pool water.Improper use of the calcium hypochlorite used for chlorination of the pool may be anothersource of scale in swimming pool waters. The directions for mixing of the hypochloritesolution should be carefully followed and care should be taken to keep the insoluble residue25

(calcium carbonate) out of the pool. The use of the chlorine gas instead of calciumhypochlorite may prove beneficial in areas with scale-forming waters.6.7 IRON REMOVALMany well waters contain iron in appreciable amounts, which will add color to the water andstain the pool. Make-up water containing iron should be added directly to the pool. Whenmixed with air and chlorine, the iron will precipitate and agglomerate into particles largeenough to be caught on the surface of the filters. Best results are obtained when smallincrements of make-up water are added over a period of time rather than once daily.6.8 ORGANIC COLORMany well waters contain organic color. When pools are filled directly with this coloredwater, the color may be so high as to prevent producing clear water. This color cansometimes be bleached by a high initial chlorine dosage. When chlorine does not remove thecolor, the re-circulation system should be started, bypassing the filters, and enough alumadded to the water to provide a dosage of about 35 ppm. After the alum has dissolved andmixed with the pool water, broadcast an equal amount of soda ash on the surface of the pool.Continue to operate the re-circulation system for an additional 2 hours, after which it shouldbe shut down and the pool allowed to stand quiescent over night. By morning a heavy flocwill be found on the bottom of the pool. Remove the settled floc with the vacuum cleanerbefore starting the filtration system. This type of treatment may also be highly effective foriron removal.Be sure that the vacuum cleaner effluent is discharged to waste and not back to the poolthrough the inlets. This will result in remixing the settled floc with the pool water.Alum is effective as a coagulant over a limited pH range. If the water is too acid, some of thealum remains in solution. When the water is too alkaline, the alum floc may tend to dissolve.The efficiency of alum as a coagulant depends on the kind and amounts of dissolved mineralsin the water supply. Hard waters coagulate quite readily over a fairly wide pH range.The coagulation of very soft, highly alkaline, colored waters prevalent in western NorthDakota may require careful adjustment of pH and the addition of a hardness element beforeproper coagulation and clarification can be accomplished. A hardness increase may beaccomplished by the addition of lime (calcium carbonate) or calcium chloride. Calciumchloride will increase the hardness without increasing the alkalinity.6.9 CLOUDY WATEROccasional cloudiness of the swimming pool water occurs even when the filters andchlorination equipment are being operated in a proper manner. Cloudiness of the pool watermay be due to many sources.26

A. Cloudiness of the water in pools using diatomaceous earth filters may be dueto filter aid passing directly into the pool water. Check the fabric covering thefilter elements for holes or tears. If the fabric is in good condition, check to besure that the proper grade of diatomaceous earth is being used.B. Water may turn cloudy when soda ash is dumped directly into the pool. Theaddition of the soda ash causes a sudden rise in the pH of the water at thepoint of addition and may cause precipitation of calcium and magnesiumcarbonates. Soda ash should be added continuously to the pool water bymeans of a proportioning pump. If a pump is not available, the soda ashshould be added in small increments, rather than in one large application tominimize precipitation.C. Very soft, alkaline waters will remain turbid in spite of all efforts of the pooloperator. This is due to the absence of calcium and magnesium in the water.The total hardness of the water may have to be adjusted to at least 50 ppm toobtain adequate water clarity. The total hardness of the water may beincreased without an increase in alkalinity by adding calcium chloride.6.10 ALGAE CONTROLAlgae are microscopic plants that grow in water. The spores of algae are carried in the airand are deposited in a swimming pool during a wind storm, dust storm, or rain. In the water,algae spores grow, using carbon dioxide, nitrogen, and phosphorous and other availableelements. When exposed to sunlight, these cells multiply at a very rapid rate. If the algae areallowed to grow, the pool will take on a disagreeable appearance and turbidity may increaseto a point where the bottom is completely invisible, even at the shallow end of the pool. Thishigh turbidity is a definite safety hazard to all persons using the pool facilities. Algae alsotend to raise the pH of the pool water through the use of dissolved carbon dioxide.There are countless species of algae, each with a different resistance to chlorine, but threemain types are of concern to the pool operator:A. Black algae are the most common and persistent variety. During the earlystages of its growth, it will appear as small black (actually dark green) spotsapproximately ¼ inch in diameter. These spots will have a slippery finish andalthough seemingly fixed to the surface, they are easily removed. Simplybrush them with a stainless steel brush and super-chlorinate to prevent furthergrowth. Left to grow, they will increase in size and grip the pool wallstenaciously, actually growing into the wall. Advanced stages of black algaecan be difficult to control and require repeated brushings and large doses ofchlorine.B. Green algae first appear as a green tint in the water, almost as if the entirepool has been dyed pale green. Individual plants cannot be seen. The onset ofgreen algae can be very rapid, developing a full bloom in a matter of hours. Itis easily destroyed by superchlorinating during the early stages of growth.C. Mustard algae have a yellow-green color. It clings loosely to walls and steps.A wave of a hand through mustard algae will usually disperse it.Unfortunately, this will not destroy it, but only spread it to other areas of the27

pool. Within hours, it will be back where it was previously removed. It isquite similar to the green algae and can be removed by the same method.After treatment, the pool walls should be brushed with a stiff-bristled brush to remove thedead algae and expose any remaining living algae. If there are any stains left after brushing,they may be removed by light sanding with very fine waterproof sandpaper.Chlorine is considered the best means of killing algae. Free chlorine is an excellent algaecideand if there is a constant, and adequate, free chlorine residual, 1.0 ppm or more, algae willnot develop or grow. In pools where algae are already started, superchlorinating to about10 ppm is usually effective.In the past, copper sulfate has been used for alga control. Cooper sulfate has a number ofdisadvantages such as:A. It is ineffective in water with high alkalinity.B. It causes plugging of piping and distribution systems.C. When used in excess, it can cause green staining of bathing suits and hair.There are countless numbers of commercial products sold for alga removal. Many areeffective for this purpose, but have little or no value as disinfectants. Do not use anyalgaecide that contains ammonia or mercury compounds.Remember that free chlorine is an effective algaecide. If algae are present you mustsuperchlorinate. It cannot be overemphasized that if proper levels of free chlorine aremaintained, the pool will be free from alga problems.6.11 INSECTSInsects, particularly those that live around water, are attracted to swimming pools. The mostcommon found in pools are Hemipteras or Cleopteras (beetles) which are predaceous insectsand feed upon other insects in the pool area. They are not known disease carriers, but do biteor sting causing discomfort to the bathers.Control of insects in and around the pool is difficult, as there are no known ways ofpermanently eliminating them. Superchlorination of the pool water will kill most of those inthe pool and may drive the rest away. Most of the problem insects have wings, however, andwill return as soon as the chlorine residual is back to normal.6.12 PAINTINGOne of the outstanding assets to any pool is clear, sparkling water. This is displayed to thebest advantage by painting the walls and bottoms of the pool a light blue or white color.Paint not only makes the water appear more invigorating but also, places a smooth coating onthe concrete. An attractively painted pool is a safer pool because it is easier to keep cleanand increases the underwater visibility. Underwater swimmers stand out clearly against lightcolored walls and floors, making it easier for lifeguards to watch closely.28

One of the main reasons for painting, however, is for protection of the concrete againstwinter weather. Moisture can penetrate unprotected concrete. Alternate freezing andthawing within the pores will cause the concrete to spall off. In addition, tiny cracks willbecome enlarged and the exposed reinforcing rods will tend to rust and expand, damaging theconcrete.The most popular coatings for swimming pool use are cement base, rubber base, vinyl, andepoxy paints.A. A cement base paint will give an acceptable finish at the least cost, but it isless durable than the more expensive paints. Generally, a cement base paintcan be expected to last about one season.B. Rubber base paints cost more, but they have an appearance and durabilitysuperior to the cement base paints.C. Vinyl paints give superior finish and have a life expectancy of 1 to 2 years.Vinyl requires a spray application and, more often than not, removes it fromthe do-it-yourself category.D. Epoxy paints are expensive and difficult to apply, but they give a long lastingfinish of high quality. A professional should apply epoxy paints.The quality and durability of any paint application is substantially dependent upon thesurface to which it is applied. Applying the best of pool paints over a loose and scalingsurface will give disappointing results. Follow the directions supplied with the paint and payparticular attention to requirements regarding surface preparation.29

CHAPTER 7 - SPECIAL POOLS7.1 WADING POOLSA wading pool is a small pool for non-swimming children only and shall have a maximumdepth at the deepest point not greater than 18 inches. It shall be constructed adjacent to theswimming pool and shall be separated from it by a fence or partition sufficiently high toprevent waders from entering the swimming pool area.The water supply to the wading pool shall be filtered and chlorinated from its own separatere-circulation system or from the swimming pool re-circulation system. The outlets from thewading pool may be wasted or returned to the re-circulation system. Due to the high degreeof pollution, a wading pool shall have a maximum turnover rate of 1 hour.Wading pools work best when filled with treated water from the pool re-circulation systemand drained away through a constant level overflow. Additional chlorine may have to beadded to maintain an adequate residual. The pool shall be drained, cleaned, and refilled withfiltered and chlorinated water daily.It may be desirable to install a spray pool in lieu of a wading pool so that no water stands atany time, but is drained away as it sprays over the area.7.2 SPASTherapeutic, hydrotherapy, spa, or hot tub pools are small heated pools with roiling water,intended to be used exclusively for relaxation rather than swimming or exercise. Whirlpoolsalso provide this water action, but are usually unheated.Spas may be constructed of concrete, gunite, or fiberglass. Gunite or concrete are used mostoften when the spa is built as part of, or in conjunction with, a swimming pool built of thesame materials. Prefabricated fiberglass spas are manufactured in a wide variety of sizes anddesigns. They have molded benches, lounges, and hammocks to allow comfortable seatingor reclining. Coated with an extremely smooth gel coat finish, they can resist attacks of algaeand clean easily.The spa, or therapeutic action, derives from the warm temperature of the water and roilingaction created by the injection of air. Hydrotherapy heads or an air pump createshydrotherapy action. Hydrotherapy heads use a centrifugal pump to force water through aconstriction located in the head. An air tube connected to the throat of this constrictionprovides air and the mixture of air and water is forced out through a wall fitting into the pool.This velocity mixture of air and water provides a true massaging action.Air blowers introduce air directly into the water through hundreds of small holes built intothe pool. The roiling action provided by the blower is considerably greater than possiblewith a hydrotherapy head, but it lacks the forceful massaging action that the heads provide.30

Operating costs for a blower system are less than the costs of operating the hydrotherapyheads.Like a swimming pool, spas require a re-circulation system: a pump, a filter to remove dirt, askimmer and main drag, return inlets, a heater, and the associated piping. On a spa usinghydrotherapy heads, rather than or in addition to an air blower, a separate pump should beinstalled to provide water to the heads. Re-circulation systems should be run 6 to 8 hours aday, but the spa action is necessary only while the pool is being used. Roiling waterdissipates chlorine rapidly so it is wasteful of both energy and chemicals.Due to the small volume of water, high water temperatures (not to exceed 104ºF, 40ºC), andrapid dispersion of chlorine, a spa shall have a maximum turnover rate of 30 minutes. Sincespas contain only a small volume of water, a very small re-circulation system is usuallyadequate.All spas are self-cleaning. Turbulent action provided by the blowers or pump willimmediately throw all dirt into suspension where the filter can remove it.Chemical balance is more critical in spas because of the small volume of water involved.When adding chemicals to a spa, only very small quantities should be used. Chlorine levelsshould be kept higher than normal (consider 1.5 ppm as a minimum). The total alkalinityshould also be maintained higher than normal at 150 to 200 ppm. Chlorine should be addedto the skimmer. Acid for pH adjustment should be added directly to the pool water with theair blower on the re-circulation system turned off. This will allow the acid to mix thoroughlywith the water before contacting the pump and filter.7.3 NATURAL BATHING AREASThe use of small streams, dammed up pools along small streams, or small ponds by largenumbers of bathers is not generally recommended. Streams and rivers are continuouslycontaminated by discharges from sewage disposal systems, cesspools, barnyard wastes, andsurface draining. Mud bottoms are common which add considerable turbidity to the water,restricting underwater visibility. Streams and ponds must be considered a safety as well as ahealth hazard.Small ponds are considered a health hazard because of the small amount of diluting wateravailable. Many authorities are of the opinion that at least 500 gallons of water per batherper day should be available unless chlorination or other disinfection is maintained. Pondsshould not be used for public swimming if the surface area is less than 2 acres, or if theycontain less than 5,000,000 gallons of water.Algae growths create a considerable problem in natural bathing areas. Algae give the wateran unpleasant appearance, may cause disagreeable odors, and create a turbid condition.Treatment of large water areas with copper sulfate is not practical.31

Unless the water is being chlorinated, no insurance of the safety of the water for swimmingcan be made. While the bacterial analysis is a helpful guide, it may be of little value ingiving a definite opinion as to the freedom of the water from contamination.This department discourages development of natural bathing areas because of the numerousproblems of safety and health encountered.32

APPENDIXA-1 OFF SEASON PROTECTIONAt the close of the bathing season:A. The pool equipment should be cleaned and properly stored.B. The filters should be thoroughly washed and drained so that they will be in a cleancondition during the off season.C. Shut off the water supply and drain all lines and plumbingD. Drain the chemical feeders, hair strainer, and pumps.E. Store pool ladders and diving boards in a sheltered place. Diving boards should bestored on edge to prevent warping.F. The electrical service should be cut off and all fuses removed or circuit breakersopened.Freezing of ground water surrounding the pool is a main consideration for winter protection.Some authorities maintain that a pool properly constructed and under-drained may be safelyleft empty over the winter months. Others feel that it is better to keep the pool full of waterrather than run the risk of structural cracking resulting from leaving the pool empty. Manyauthorities recommend that the pool be kept filled with water to a level of about 18 inchesbelow the scum gutter throughout the frost period. Thus, the pressure of the water in the poolwould tend to offset the pressure against the sides and bottom. It is desirable in such casesthat logs or poles be placed in the water along the sides of the pool to absorb some of thepressure developed by the expanding ice.If the pool is to remain partially filled for winter, it is recommended that chlorine be added tothe water to prevent the growth of algae. If the water is to be used for the following season,addition of chlorine in the fall and spring to eliminate alga problems will make pool start-upmuch easier.33

A-2 POOL LOADINGA. Indoor Pools:(i) Allow 15 square feet of pool surface area per bather where the water depth isless than 5 feet.(ii) Allow 20 square feet of pool surface area per bather where the water depth isover 5 feet (excluding 300 square feet of pool surface area around each divingboard).B. Outdoor Pools:(i) Allow approximately 20 square feet of combined pool and walk surface areaper bather.(ii) Diving bays should be restricted to diving only.34

A-3 CHEMICAL DOSAGEA. Constants:1 cubic foot = 7.5 gallons (gals.)2 gallon of water = 8.34 lbs.1 ppm = 8.34 lbs. of chemical in 1,000,000 gal.1% solution (sol.) = 10,000 ppmB. Equations:(i) Pounds = ______ gal. of water x 8.34 x ppm x 1001,000,000 x % available chemical substance.(ii)Ppm = lbs. x 1,000,000 x % available chemical substanceGallons of water x 8.34 x 100(iii) Pounds = % strength of solution x gal. of sol. x 8.34% chemical purity(iv) Gallons of concentrated solution =Gals of diluted solution x % strength of diluted sol.% strength of concentrated sol.(v)(vi)Gals. Of = desired dosage (ppm) x gal. of water sol.% strength of sol. x 10,000Application = 0.378 x dosage (ppm) x flow in gpm rate (ppm).% strength of sol.C. Examples:(i)How many pounds of 65% available chlorine are needed to give a 0.8 ppmchlorine residual in 180,000 gallons?Lbs. = 180,000 gal. x 8.34 x 0.8 ppm x 100 = 1.85 lbs.1,000,000 x 65% available chlorine(ii) How many milligrams per liter of a chemical solution would result if 1.5pounds of gas chlorine were added to 160,000 of water?Ppm = 1.5 lbs. X 1,000,000 x 100% = 1.12 ppm chlorine160,000 gal. x 8.34 x 100(iii)Prepare 5 gallons of 1% chlorine solution from calcium hypochloritecontaining 65% available chlorine.35

Pounds = 1% x 5 gal. x 8.34 – 0.64 poundsRequired 65%(iv)Prepare 50 gallons of 1% chlorine solution from sodium hypochloritecontaining 5.25% available chlorine.Gallons of = 50 gal. x 1% - 9.5% gallons5.25% solution 5.25%(v)A swimming pool contains 50,000 gallons of water. How much laundrybleach (5.25% chlorine) must be added to the water to obtain a dosage of 2.0ppm?Gallons of = 2 ppm x 50,000 gal. – 1.9 gal.Laundry bleach 5.25% x 10,000(vi)Determine the number of milliliters per minute of a 2% chlorine solution to beadded to a water flow of 275 gpm to obtain a chlorine dosage of 1.5 ppm.Application = 0.378 x 1.5 ppm x 275 gpm – 78 ml/minRate (ml/min) 2%36

A-4 SUPERCHLORINATIONApproximate chlorine quantities required to establish 8 mg/l: (pt. = pint; gal. = gallon;oz. = ounce)Pool Capacity(gallons)Ordinary HouseholdBleach (5.25%)Liquid Chlorine(10%)CalciumHypochlorite (65%)1,000 1 pt. 0.5 pt. 2 oz.5,000 5 pt. 2.5 pt. 8 oz.10,000 1 gal. 2 pt. 5 pt. 1 lb. 0 oz.15,000 1 gal. 7 pt. 7 pt. 1 lb. 8 oz.20,000 2 gal. 4 pt. 1 gal. 2 pt. 2 lb. 0 oz.25,000 3 gal. 1 pt. 1 gal. 5 pt. 2 lb. 9 oz.30,000 3 gal. 6 pt. 1 gal. 7 pt. 3 lb. 1 oz.40,000 5 gal. 2 gal. 4 pt. 4 lb. 2 oz.50,000 6 gal. 2 pt. 3 gal. 1 pt. 5 lb. 2 oz.37

A-5 CHLORINATOR SETTINGSGas chlorinator settings to feed 1.0 ppm chlorine at various flow rates:Flow Rate Feed Rate Flow Rate Feed Rate(gpm) (lbs/24 hour) (gpm) (lbs/24 hour)10 0.12 160 1.920 0.24 180 2.230 0.36 200 2.440 0.48 220 2.650 0.60 240 2.960 0.72 260 3.170 0.84 280 3.480 0.96 300 3.690 1.08 325 3.9100 1.2 350 4.2120 1.4 375 4.5140 1.7 400 4.8To obtain a setting for other than 1.0 ppm, multiply the chart setting by the dosage desired.A-6 SAFETY RULES FOR GAS CHLORINE EQUIPMENTA. Be sure of what you are doing when handling chlorine.B. All threaded fittings and the valve stem have right hand threads. Turnclockwise to close or tighten.C. Always use a new gasket of standard material for connection of cylinders andequipment.D. The cylinder valve wrench should be 3/8-inch square box with a maximumlength of 6 inches. The wrench shall be left on the valve stem of the chlorinecylinder in use at all times.E. Frequently check for leaks from the equipment. Locate these leaks by the useof ammonia, not smell.F. If a chlorine leak is detected, repair it at once. Chlorine leaks get worse withtime.G. Take time to complete the job properly and safely.H. Keep your eyes open – be alert for danger.I. Return cylinders to the supplier as soon as they are empty.J. Remember that you are responsible for the proper operation of the equipment.38

A-7 DECHLORINATIONSodium sulfite, sodium bisulfate, or sodium thiosulfate can be used when it is necessary tode-chlorinate swimming pool water. The dry compounds may be applied by broadcastingevenly over the surface of the pool water. Solutions of the compounds may also be preparedand added to the pool near the inlets to insure mixing.Sodium sulfite and sodium bisulfites are toxic materials and should be handled with care.They may react with water to produce toxic and corrosive fumes of sulfur dioxide. Sulfitesand bisulfates are rapidly oxidized to sulfates and, when used in proper amounts, should notbe hazardous to bathers. Do not, however, permit swimming while de-chlorinating withsulfite compounds.Sodium thiosulfite is considered low toxic material. The appropriate dosage for removal of1.0 ppm of excess chlorine is as follows:Chemical CompoundPounds per 25,000 gallonsSodium Sulfite 0.75Anhydrous Sodium Sulfite 0.40Sodium Bisulfite 0.42Sodium Thiosulfite 0.25Example: To remove 8 ppm chlorine from 250,000 gallons of swimming pool water withsodium thiosulfite, how many pounds are needed?8 ppm x 0.25 lbs x 250,000 gal = 20 pounds25,000 galA-8 TESTING CHLORINE RESIDUALSNearly all tests for residual chlorine in swimming pool water are accomplished with acolorimeter, a device that compares colors of solutions with color standards prepared in alaboratory.Orthotolidine (OTO) has been used for 40 years or more in what is referred to as the flashtest method. However, it is obsolete and has been proven to be toxic. Therefore, it has beenreplaced by a far more accurate and reliable test called the DFD method. DFD, as a liquid ora powder, is the only accurate way to determine chlorine residuals.The following rules should apply to all chemical testing apparatus:A. Follow directions carefully. Be particularly accurate in measuring amounts ofreagents and in observing time and temperature requirements.B. Be scrupulously clean. Be sure all solution tubes, eyedroppers, reagentbottles, and equipment are rinsed thoroughly after each use, both inside andoutside. Do not handle the equipment with dirty hands. Rinse off39

immediately any reagents that touch the skin. Store the equipment, properlyboxed or encased, in a clean, protected place. Do not interchange parts suchas solution tubes, bottle caps, or droppers.C. Be sure all reagents are fresh and that the same manufacturer who made thecolor samples has supplied them. Each manufacturer develops reagents,which are compatible with his/her own instruments, and not all reagents of thesame name are of equal composition or concentration. Reagents lose theirstrength on aging and exposure to light and should not be kept longer thanrecommended by the manufacturer.D. Avoid subjecting color standards and reagents to prolonged direct sunlight, ortemperatures over 100 degrees or below freezing.A-9 TESTING pHThe determination of pH is based on the ability of certain organic materials called indicatorsto change color with the change in acidity or alkalinity of the water. Addition of a smallamount of indicator to a sample of the pool water and comparing the color developed withthe color standards representing the various pH values permits a rapid measurement of thepH to be made.Waters containing high free chlorine residuals may have a bleaching effect on the indicatorand cause errors in the pH determination. Adding a small crystal of a de-chlorinating agent(about the size of a grain of rice) such as sodium thiosulfate to the sample prior to addition ofthe indicator will remove the excess chlorine.The procedure suggested for the pH determination is essentially the same with most testcomparisons. Please use the volume of water sample and pH indicator as specified in the testkit instructions.A-10 BACTERIOLOGICAL TESTINGIn the bacteriological analysis of swimming pool water, the laboratory does not attempt toisolate and identify any particular type of disease-producing bacteria. To do this would be avery long and difficult task and the result would not be entirely meaningful. Instead, the lablooks for a particular group of bacteria which is known as coliform bacteria. These bacteriaare normally found in the intestines of man and other warm-blooded animals as well as inbirds. The presence of such bacteria in water indicates that the water is being contaminatedwith some sewage-like material. Obviously, such a situation indicates an unsafe condition asdisease-producing organisms could be present at any time.Under Article 13-10 of the Fargo Municipal code, public pool facilities are required to besampled weekly and monthly for semi-public facilities. A certified laboratory must analyzeall samples.40

Samples should be collected only when the pool is in use and preferably during periods ofheaviest swimmer load. The sampling point should be varied from time to time to obtain arepresentative cross-section of the sanitary quality of the pool water.In order to secure a true picture of the condition of the swimming pool water at the time ofsampling, sodium thiosulfite is employed to neutralize the chlorine residual in the waterduring transportation to the laboratory.To sample the pool, carefully remove the cap from the bottle without touching the innersurface of the bottle or cap. The open bottle is then plunged beneath the surface of the waterand swept forward until full. Leave a small air space at the top of the bottle and replace thecap. Do not rinse the bottle with pool water as this will remove the sodium thiosulfite thathas been added.A-11 ENCLOSURE FOR SWIMMING POOL CHLORINATORSIn all pools, where chlorine is supplied by means of a vacuum-operated gas chlorinator,which provides automatic shut off of the gas in case of water pressure failure, a leak, or abreak in the chlorine piping, the chlorine cylinders, chlorinator, and all appurtenances shallbe located in a separate, reasonably gas-tight, vented enclosure or room. The room shall beat ground level to permit easy access to all equipment. The door of the room should open tothe outside and should not open toward the swimming pool or equipment area. Theenclosure may be constructed of metal, concrete block or other fire resistant material. Afresh air intake vent shall be installed near the top of the enclosure. A window of at least 18inches square and artificial illumination shall be provided so the operation of the equipmentmay be observed at all times without entering the enclosure. Electrical switches for thecontrol of lighting and ventilation shall be located on the outside of the enclosure adjacent tothe door.When the enclosure is part of the filter room or other building, forced air ventilation of theenclosure is required. The exhaust fan shall be capable of one or more air changes perminute. The fan should be equipped with an intake duct extending to near floor level and theair should be exhausted to an outside area where chlorine gas will not create a health hazard.Please note the following (see illustration on page 46):A. The chlorine cylinders shall be secured to the enclosure wall with a safetychain to prevent tipping.B. The chlorine cylinder operating valve shall be opened no more than onequarter to one-half turn.C. The special wrench for operation of the chlorine cylinder valve shall beattached to the operating stem of the valve at all times.D. A platform scale shall be supplied for weighing the chlorine cylinder. This isthe only way that the operator can determine the amount of chlorine consumedduring a 24-hour period.E. A gas mask approved by the Bureau of Mines for protection against chlorine,or an approved air pack shall be mounted outside the chlorine room.41

F. A bottle of ammonium hydroxide shall be available for checking for chlorineleaks.G. A chlorine cylinder repair kit should be available for emergency use.A-12 INJECTOR LOCATION FOR VACUUM-OPERATED CHLORINATORSMost vacuum operated-gas chlorinator problems have been due to improper location of theinjector, resulting in insufficient water pressure to develop the necessary vacuum foradequate chlorine flow. The point of chlorine injection on a swimming pool filter recirculationline should be carefully chosen so that the water pressure at this point is as low aspossible. The injector uses a water jet to create a vacuum and will work satisfactorily only ifthere is enough pressure on the water supply to the nozzle to create a strong jet action.Adequate pressure for operation of the chlorine injector may be obtained by installing theinjector on the suction side of the re-circulation pump and connecting the injector watersupply to the pressure side of the re-circulation pump. The pressure differential developedacross the pump is more than adequate for proper operation of the gas chlorinator42

A-13 RECOMMENDED SWIMMING POOL OPERATIONAL STANDARDSA. Operate the re-circulation system continuously (24 hours per day) to insureclarity of the pool water.B. Maintain pH values between 7.4 and 7.8.C. Maintain a free chlorine residual of at least 1.0 mg/l.D. Maintain the pool and related facilities in a clean manner at all times.E. Keep the pool surface free of film and floating dirt and the pool bottom free ofsediment.F. Scrub the bathhouse floors daily with hot soapy water followed by a liberalapplication of ¼ to 1-% chlorine solution.G. Inspect all patrons and exclude those showing symptoms of infection.H. Require all patrons to take a nude shower using warm water and soap beforeentering the pool.I. Keep a daily record of operation of the re-circulation system, chemicaladditions, pH, chlorine residuals, and bathing load.J. Collect weekly samples of the pool water and submit to the nearest laboratoryfor bacterial analysis.THERE IS NO SUBSTITUTE FOR CLEANLINESS44