pH Levels in Pool Water
The pH levels in pool water play a large part in the balance of the water. Filters and disinfection clean your pool water, but the pH is affected by other factors, such as dirt, oil, swimmer wastes, cosmetics and rain. The pH level is an indication of whether your pool water is acidic or basic. Total alkalinity and calcium hardness are also important to the balance of the water in your pool.
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High pH
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Neutral pH is 7 on a scale of 0 to 14. Levels below 7 are acidic and levels above 7 are alkaline (basic). The Pool Center recommends testing the pH of your pool daily. The range of pool water should be between 7.4 and 7.6. If the pH level is over 7.8, the water condition is scale-forming and you'll need to add acids, such as hydrochloric acid or sodium bisulfate to restore a neutral level. A high pH level results in inefficient chlorine activity, discoloration of walls, cloudy water, eye irritation and overworking the filter.
Low pH
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A pH level below 7.2 means your water is corrosive (acidic) and you'll need to add bases, such as sodium carbonate or sodium hydroxide, to correct it. The amounts needed depend on the pH level and number of gallons of water in your pool. The consequences of a low pH include rapid dissipation of chlorine residuals, eye irritation, corrosion of pump, heater core and metal fitting, stains from dissolved metal, etching in plaster walls and rapid alkalinity loss.
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Total Alkalinity
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Total alkalinity is a measurement of the water's ability to prevent pH changes. The total alkalinity level should be kept between 80 to 150 parts per million (ppm). You should test it weekly, advises the Pool Center. When this level is low, it allows rapid pH changes when impurities or chemical are introduced to the water. If total alkalinity is too high, it makes it more difficult to adjust pH levels. Alkalinity is increased by adding sodium bicarbonate (baking soda). High levels are lowered by adding an acid.
Calcium Hardness
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Calcium hardness refers to the amount of dissolved calcium salts in your pool water, and you should test it weekly. The North Carolina Division of Environment Health indicates that 250ppm is ideal for a plaster pool, although the acceptable range is wide. Very low levels can result in leaching of calcium from the walls of the pool, leaving pits in the plaster. High levels result in cloudy water and can cause the formation of scales. Calcium chloride is used to increase calcium hardness. It is lowered by the addition of anhydrous trisodium phosphate.
Considerations
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Keeping a proper pH balance of your pool water is important maintaining safe use of the pool. Aside from balanced pH, alkalinity and calcium hardness, you'll need disinfectant to destroy harmful organisms and algaecide to prevent or kill algae.
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References
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