Design Guide for Community Water Systems - The Water, Sanitation ...

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in areas served by rural water districts. The normal working pressure in thedistribution system should be approximately 60 psi.8.1.2. Diameter.a. The minimum size of a water main for providing fire protection andserving fire hydrants shall be six inches in diameter. Larger mains shall berequired, if necessary, to allow withdrawal of the required fire flow whilemaintaining the minimum residual pressure of 20 pounds per square inchthroughout the distribution system.b. For public water systems not providing fire protection, no main shall besmaller than two inches in diameter.8.1.3. Fire ProtectionWhen fire protection is to be provided, system design should be such that fireflows and facilities meet the classification criteria of the state InsuranceServices Office (ISO). Water mains not designed to carry fire-flows shall nothave fire hydrants connected to them.8.1.4. Flushing.a. Flushing devices and valving shall be provided to allow every main in thedistribution system to be flushed. Flushing devices should be sized toprovide flows that will give a velocity of at least 2.5 feet per second in thewater main being flushed.b. In order to provide increased reliability of service and reduce head loss,dead ends shall be minimized by making appropriate tie-ins wheneverpractical.c. Where dead-end mains occur, they shall be provided with an approvedflushing device.d. No flushing device shall be directly connected to any sewer.8.2. Valves.Sufficient valves shall be provided on water mains so that inconvenience and sanitaryhazards to customers will be minimized during repairs. Valves should be located atnot more than 500 foot intervals in commercial districts and at not more than oneblock (or 800 foot) intervals in residential or other districts. Where systems servewidely scattered customers and where future development is not expected, the valvespacing should be at every water main branch on both the feeder main and the branchline.Aug. 29, 2003Page 150
8.3. Fire Hydrants.8.3.1. Location and spacing.Hydrants should be provided at each street intersection and at intermediatepoints between intersections to meet the classification criteria of the state ISO.Generally, hydrant spacing may range from 350 to 600 feet, depending on thearea being served.8.3.2. Valves and nozzles.Fire hydrants should have a minimum bottom valve size of at least five inches,one 4-1/2 inch pumper nozzle, and two 2-1/2 inch nozzles.8.3.3. Hydrant leads.The hydrant lead shall be a minimum of six inches in diameter and contain ashutoff valve.8.3.4. Drainage.A gravel pocket or dry well shall be provided unless the natural soils willprovide adequate drainage for the hydrant barrel. Hydrant drains shall notbe connected to or located within ten feet of sanitary sewers or stormdrains.8.4. Air Relief Valves; Valve, Meter and Blow-Off Chambers8.4.1. Location.At high points in water mains where air can accumulate, provisions shall bemade to remove the air by means of manually operated hydrants or automaticair relief valves. Automatic air relief valves shall not be used in situationswhere flooding of the manhole or chamber may occur.8.4.2. Piping.The open end of an air relief pipe from automatic valves shall be extended toat least one foot above grade and provided with a screened, downward-facingelbow. The pipe from a manually operated valve shall be capped with athreaded removable cap or plug and should be extended to the top of the pit.Vaults or wells housing automatic air relief valves shall be drained to daylightwith drains sized to carry the maximum output of the air relief valve.8.4.3. Chamber drainage.Chambers, pits, or manholes containing valves, blow-offs, meters, or othersuch appurtenances to a distribution system, shall not be connected directly toany storm drain or sanitary sewer, nor shall blow-offs or air relief valves beAug. 29, 2003Page 151
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Design GuideforCommunity Water Syst
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2.18. AUTOMATION. .................
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4.3.11. Waste Disposal. ...........
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CHAPTER 6 -- MINIMUM CONSTRUCTION R
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Maximum Hour Demand -- The amount o
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and deviations are subject to indiv
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(blank)Aug. 29, 2003Page viii
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a. A description of the nature and
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a. Hydrological data, stream flow,
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4. Be conducted under the same oper
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maintaining the new technology and
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1.2.1. Plans shall include:a. Suita
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name, number, effective date, publi
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e. The site will provide all-weathe
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chlorine residual by methods in "St
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etween them, a six-inch band of con
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a. Regulated recreational activitie
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e done to determine the degree and
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1. Pumping rate;2. Pumping water le
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sieve analyses of the water bearing
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e circulated in the annular space s
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emoved. Therefore, every well shoul
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3.2.6.4. Pitless well units.a. The
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SIZE (inches)6 id.8101214 od.161820
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Chapter 4 -- Tre atment4.0. General
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settling basins shall be not less t
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3. Shall have valves located outsid
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d. Be automatic. Timers on automati
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2. Uniformity coefficient not great
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j. During air scour, the backwash w
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. An easily readable meter or flow
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4.3.4. Design Pressure Drop or Tran
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4.3.9. Flow Meters.Totaling rate of
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utilized, shall be 1.0 milligrams p
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. Removal of precursors prior to ch
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5. Consideration shall be given to
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. Pre-treatment requirements. Iron,
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t. Housing. Bagged salt and dry bul
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4.7. Iron and Manganese ControlIron
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Where phosphate treatment is used,
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3. Series and parallel flow piping
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approval of the department before u
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contact time must be provided to co
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a. Sanitary sewers with the approva
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1. Obtain a letter of approval from
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6. The provisions for the final dis
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a. Missouri River or Mississippi Ri
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5.0.3. General equipment design.Gen
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minimize chemical dust created by t
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Page 126 and 127: 5.4.2. Acids.a. Acids shall be kept
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Page 148 and 149: 6.4.2.2. Suction lines.Suction line
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Page 172 and 173: 8.6.5. Force mains.There shall be a
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