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Pool Care Guide: Water Balance

Water Balance is a term used to describe the interaction of pH, Total Alkalinity and Calcium Hardness, and their overall effect on your pool equipment, water quality and the pool itself. We will discuss each factor separately and then as a whole.


pH is a measurement of the relative acidity and basicity (alkalinity) of water. pH is measured on a scale that runs from 0 to 14. pH values below 7 are acidic and values higher than 7 are basic (alkaline). AQUA pH Minus has a pH of 1.5 and is used to lower the pH of pool water. AQUA pH Plus has a pH of 11.5 and is used to raise the pH of pool water. Your pool water should always have a pH in the range of 7.4 to 7.8.

Ideal Range: 7.4 - 7.6

High pH can cause: eye irritation, cloudy water, scaling, and inefficient use of sanitizers.

Low pH can cause: eye burn, etched plaster, corrosion and staining.

Total Alkalinity

Total Alkalinity refers to the amount of alkaline material (carbonates, bicarbonates and hydroxides) in your pool water. Pool water with low TA is sensitive to a change in pH. The pH will "bounce" from high to low and back up again very quickly. Pool water with too high a TA is very resistant to a change in pH making it difficult to adjust pH when necessary.

The proper range of TA is 120 to 150 ppm in plaster or marbalite finished pools and 125 to 175 ppm in fibreglass, vinyl-lined or painted pools.

Ideal Range: plaster:100 - 150 ppm, vinyl:125 - 175 ppm

High TA can cause: eye irritation, cloudy water, scaling, and make pH difficult to adjust

Low TA can cause: eye burn, etched plaster, corrosion and staining.

Calcium Hardness

Total Hardness refers to the amount of calcium and magnesium carbonate in water. In pool water chemistry we are interested only in the calcium hardness (CH) of your pool water.

You should test for CH at opening, mid-season and just before closing your pool for the winter. If your pool is open all year, test for CH every 3 months.

Ideal Range: plaster:225 - 300 ppm, vinyl:175 - 250 ppm

High CH can cause: cloudy water, scaling

Low CH can cause: etched plaster, corrosion and staining.


Sunlight can rapidly destroy chlorine residual in outdoor pools unless the chlorine is stabilized. Stabilization refers to the ability of the sanitizing chemical to resist deactivation by sunlight. If the chlorinating chemical is stabilized, this process is slowed significantly and the chlorine remains effective longer, even in bright sunlight.