Swimming Pool Codes - City of Fargo

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