Swimming Pool Codes - City of Fargo

(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