Chemicals used in Swimming Pools:
Proper water chemistry is essential to maintaining safe and consistent swimming pool operation. Chemicals used in swimming pools include: Disinfectants to destroy harmful or otherwise objectionable organisms; Alkalinity and pH Adjusters to maintain a consistent acid-base relationship and acid buffering capacity; Chlorine Stabilizer to prevent unnecessary loss of chlorine; Algicide to kill and prevent algae, and Filter Aids to help remove foreign material. Following is a discussion of various factors which affect water chemistry, how they affect swimming pools and how to use pool chemicals to restore a properly balanced water chemistry.
Calcium hardness is a measure of the dissolved calcium salts in water. Under normal conditions this should not be a problem in properly operated swimming pools. Estimates of the proper range of calcium hardness vary widely but the ideal level for plaster pool is generally considered to be about 250 ppm. If calcium hardness is very low then water may leach calcium from pool walls causing pitting of the plaster surface. Very high calcium hardness may contribute to scale formation and clouding of the water. To raise calcium hardness – add calcium chloride.
Chart No. 8 – Raising Hardness With Calcium Chloride
GALLONS IN POOL
|10||2 oz.||10 oz.||1 1/4 lbs.||1 3/4 lbs.||2 1/2 lbs.||3 1/4 lbs.||6 1/4 lbs.|
|20||4 oz.||1 1/4 lbs.||2 1/2 lbs.||3 3/4 lbs.||5 lbs.||6 1/4 lbs.||12 1/2 lbs.|
|30||6 oz.||1 3/4 lbs.||3 3/4 lbs.||5 1/2 lbs.||7 1/2 lbs.||9 1/2 lbs.||18 3/4 lbs.|
|40||8 oz.||2 1/2 lbs.||5 lbs.||7 1/2 lbs.||10 lbs.||12 1/2 lbs.||25 lbs.|
|50||10 oz.||3 lbs.||6 1/4 lbs.||9 1/2 lbs.||12 1/2 lbs.||15 3/4 lbs.||31 1/4 lbs.|
|60||12 oz.||3 1/4 lbs.||7 1/2 lbs.||11 1/4 lbs.||15 lbs.||18 3/4 lbs.||37 1/2 lbs.|
|70||14 oz.||4 1/4 lbs.||8 3/4 lbs.||13 lbs.||18 3/4 lbs.||22 lbs.||43 3/4 lbs.|
|80||1 lb.||5 lbs.||10 lbs.||15 lbs.||20 lbs.||25 lbs.||50 lbs.|
|90||1 lb.||5 1/2 lbs.||11 1/4 lbs.||17 lbs.||22 1/2 lbs.||28 lbs.||56 1/4 lbs.|
|100||1 1/4 lbs.||6 1/4 lbs.||12 1/2 lbs.||18 3/4 lbs.||25 lbs.||31 1/4 lbs.||62 1/2 lbs.|
To lower calcium hardness anhydrous trisodium phosphate may be used. One pound trisodium phosphate per 10,000 gallons will lower calcium hardness 11 ppm. Use in small increments or clouding may occur. Another method of lowering calcium hardness is to simply drain off part of the pool water and dilute the remaining water with fresh make up water.