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How to lower pH in a pool
If pH is above 7.8, chlorine is working poorly and scale can form. Muriatic acid is the usual fix, and dry acid is a gentler option to handle.
Steps
- Test pH and alkalinity.
- Pour acid slowly into the deep end, near a return jet, with the pump running. Never add water to acid.
- Run the pump for at least an hour and retest.
- Repeat with a smaller dose if needed.
How much muriatic acid
| Pool size | 7.8 to 7.4 | 8.2 to 7.4 |
|---|---|---|
| 5,000 gal | 5 fl oz | 8 fl oz |
| 10,000 gal | 10 fl oz | 15 fl oz |
| 15,000 gal | 15 fl oz | 23 fl oz |
| 20,000 gal | 20 fl oz | 31 fl oz |
| 30,000 gal | 30 fl oz | 1.4 qt (46 fl oz) |
At 100 ppm alkalinity. These are estimates: use the pH calculator with your own alkalinity.
Why pH keeps rising
- High alkalinity keeps pushing pH up as carbon dioxide leaves the water.
- Waterfalls, spa spillovers and salt cells add aeration or raise pH directly.
- Liquid chlorine and cal-hypo raise pH slightly with each dose.
If you are adding acid every few days, bring alkalinity down instead of chasing pH.
Add chemicals to water, never water to chemicals, one at a time, with the pump running. Wear gloves and eye protection, and never mix products.