Total Alkalinity Total alkalinity is the measure of how stable the ph is. It measures the pool water s buffering capacity to resist ph changes. Without control of the total alkalinity, the ph will rise and fall abruptly. The ability to resist this change in ph is due to the presence of bicarbonate and carbonate ions and other compounds. According to the Indiana State Department of Health, Public and Semi-Public Swimming Pools Rule 410 IAC 6-2.1, total alkalinity shall be kept between 80 and 120 ppm. A low total alkalinity makes it difficult to maintain a desired ph and can lead to corrosive water, which can damage equipment. Green water can also be another symptom of low alkalinity. To increase the alkalinity level, add sodium bicarbonate, typically packaged as Alkalinity Increaser or Alkalinity Plus. High levels of total alkalinity can cause the ph to get stuck and is difficult to change. High total alkalinity can also cause cloudy water and scale formation. To decrease the alkalinity level, sodium bisulfate or muriatic acid can be added to the pool water these are the same chemicals used to lower ph. TOO LOW Low ph Corrosion ph Fluctuation Ideal 80-120 ppm TOO HIGH Difficulty Adjusting ph Cloudy Water High ph
Calcium Hardness Calcium hardness involves measuring the hardness of minerals, such as calcium, in the water. The calcium in the water is naturally occurring due to leaching process when ground water comes in contact with rocks and soils containing calcium. The ideal range for calcium hardness, according to the Pool & Spa Operator Handbook, is 200 to 400 ppm (mg/l). When balancing calcium saturation, ph, total alkalinity, temperature and total dissolved solids must be considered. If the calcium hardness is too low, the water can become corrosive and etch the surface of the pool. Metals in the pool equipment, pipe fittings and pump connections can corrode and this will result in the staining of the walls and floor of the pool. Calcium chloride can be used to increase the calcium hardness of the water. If the calcium harness is too high, the water can become scale forming on the pool surfaces. The filter and pipes can become clogged which will reduce the water flow and circulation. The water will become cloudy and swimmers will complain of eye and skin irritation. Lowering calcium hardness is very difficult. The process can involve partially draining the pool and replacing existing water with source water that has a lower level of harness. Fill water can be filtered through a water softener to reduce the hardness. Lowering the ph and total alkalinity to compensate for high calcium hardness levels will help to maintain a balanced saturation index. TOO LOW Etching of Plaster Aggressive corrosive water Pitting Surfaces Ideal 200-300 ppm Usual Range 175-500 ppm TOO HIGH Scale Formation Cloudy Water Filter Calcification Reduced Circulation Rough Surfaces Eye Irritation
Langelier Index The Langelier index, or saturation index, is one of several methods of calculating calcium saturation. The index uses the ph, total alkalinity, calcium hardness, temperature and total dissolved solid levels. The relation of these allows us to determine calcium saturation. The Langelier index, used here, is one the health departments will most often use. The calculation uses the ph of the water as is, add factors off the table below for total alkalinity, calcium harness and temperature. Total dissolved solids do not change the calculation much, and are often used as a constant of 12.1. If the TDS is over 1000 ppm the constant can be changed to 12.2. According to the Pool & Spa Operator Handbook, values between +0.3 and 0.3 are considered balanced. Negative values are corrosive. Positive values are scale forming.
Chlorine Characteristics CHARACTERISTICS OF CHLORINES GAS CHLORINE SODIUM HYPOCHLORITE CALCIUM HYPOCHLORITE LITHIUM HYPOCHLORITE DICHLOR TRICHLOR % AVAILABLE CHLORINE 100% 12-15% 65-70% 35% 56% OR 62% 90% ph EFFECT Lowers (ph <1.0) Raises (ph 13.0) Raises (ph 11.8) Raises (ph 10.7) Neutral (ph 6.9) Lowers (ph 2.9) LOST TO SUNLIGHT YES YES YES YES NO NO PHYSICAL APPEARANCE Gas Liquid Granular & Tablets Powder Granular Granular & Tablets
Pool Chemical Formulas Pool Type: (ie spa, pool, wading, etc ) Gallons: Pool Occupancy: Increase Chlorine Calcium Hypochlorite Sodium Hypochlorite Lithium Hypochlorite Decrease Chlorine Sodium Sulfite Sodium Thiosulfate (dechlor) Increase ph Sodium Carbonate (Soda Ash) Caustic Soda Decrease ph Muriatic Acid/Hydrochloric Acid Sodium Bisulfate Increase Total Alkalinity Sodium Bicarbonate (Baking Soda) Decrease Total Alkalinity Muriatic Acid/Hydrochloric Acid Sodium Bisulfate.125 x ppm change x pool volume 10,000 = pounds.1016 x ppm change x pool volume 10,000 = gallons.250 x ppm change x pool volume 10,000 = pounds.2 x ppm change x pool volume 10,000 = pounds.0625 x ppm change x pool volume 10,000 = pounds.186 x ppm change x pool volume 10,000 = pounds.094 x ppm change x pool volume 10,000 = pounds.5 x ppm change x pool volume 10,000 = gallons.05 x ppm change x pool volume 10,000 = pounds.15 x ppm change x pool volume 10,000 = pounds.016 x ppm change x pool volume 10,000 = gallons.16 x ppm change x pool volume 10,000 = pounds Decrease Stabilizer Drain and fill with fresh water Basic conversion *dry and liquid Conversions are not interchangeable* 1 lb (pound) = 16 ounces (Dry) 128 fl.oz. = 1 gallon (Liquid)