High pH makes chlorine sluggish and water cloudy. Here's how to bring it down safely with muriatic acid — and the exact amount for your gallons and alkalinity.
Ideal pool pH is roughly 7.4–7.6. Above about 7.8, chlorine loses effectiveness, water can cloud, and scale can form. The calculator above opens on the Lower pH mode — enter your gallons, current pH, and total alkalinity for the muriatic acid dose.
Muriatic acid (typically 31.45%) is the usual tool. Always add acid to water, never the reverse: pre-dilute in a bucket of pool water and pour it slowly around the deep end with the pump running. Never add acid at the same time as chlorine — even the fumes react dangerously; separate them by several hours. For a large correction, add about two-thirds of the dose, circulate 4–6 hours, retest, then finish. This avoids overshooting into low pH, which is its own problem to reverse.
Adding acid lowers both pH and total alkalinity. If your alkalinity is also high, that's fine — the acid helps both. If alkalinity is already low, lower pH gently and retest, because you may need to rebalance. When pH keeps drifting up, persistently high alkalinity is often the real driver.
Roughly 7.4 to 7.6. Below that, water can become corrosive; above about 7.8, chlorine weakens and scale and cloudiness become likely, which is when you'd lower it.
It depends on your pool volume, current pH, and total alkalinity, because alkalinity buffers the change. Enter those in the calculator above for a specific amount, and split large doses: add about two-thirds, retest, then finish.
Persistently high total alkalinity is the usual cause; it pushes pH back up after you correct it. New plaster, aeration features, and some sanitizers also raise pH. If it climbs constantly, lowering alkalinity into range often stabilizes pH.