Proper water chemistry is essential to maintaining safe and consistent swimming pool operation. pH is an important part of this chemistry. If your pH is too low your pool water may become acidic, chlorine residuals dissipate rapidly, eye irritation may occur as well as corrosion to metal fittings, pump impellers, and heater cores. Low pH also causes a rapid loss of alkalinity.
To avoid the problems listed above, pH must be maintained between 7.2 and 7.8. The most desirable level for pH is between 7.4 and 7.6. If pH is too low - run alkali demand test if available. Raise pH by adding soda ash (sodium carbonate). Never add more than 2 lbs per 10,000 gallons in a single treatment. Be sure the pump is running when chemicals are added. Allow to recirculate then retest to determine if further treatment is necessary. Caustic soda (sodium hydroxide) is sometimes used with chemical feed pumps to raise pH. If problems with low pH persist, it may be necessary to raise total alkalinity to stabilize the pH.
Raising pH with Soda Ash
(If pH is under 7.4, add this amount of soda ash, then retest)
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GALLONS IN POOL |
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pH |
1,000 |
5,000 |
10,000 |
15,000 |
20,000 |
25,000 |
50,000 |
|
7.2-7.4 |
2/3 oz. |
3 oz. |
6 oz. |
9 oz. |
12 oz. |
1 lb. |
2 lbs. |
|
7.0-7.2 |
3/4 oz. |
4 oz. |
8 oz. |
12 oz. |
1 lb. |
1 1/4 lbs. |
2 1/2 lbs. |
|
6.6-7.0 |
1 1/4 oz. |
6 oz. |
12 oz. |
1 lb. |
1 1/2 lbs. |
2 lbs. |
4 lbs. |
|
Under 6.7 |
1 1/2 oz. |
8 oz. |
1 lb. |
1 1/2 lbs. |
2 lbs. |
2 1/2 lbs |
5 lbs |