How to Lower pH in a Pool
High pool pH causes scale, cloudiness, and weak chlorine. Here's how to lower it with acid — and why alkalinity is part of the fix.
Updated June 2026
Quick answer
Lower pool pH with muriatic acid or a dry acid (sodium bisulfate), added to circulating water and re-tested after it mixes. Target 7.2–7.8. Acid lowers total alkalinity too, so check both — and add it gradually with the pump running, never to a still pool.
Why high pH is a problem
- Weak chlorine — sanitizer loses much of its punch as pH rises, so the water gets harder to keep clear.
- Scale and cloudiness — minerals fall out of solution, hazing the water and crusting surfaces, the heater, and salt cells.
- Irritation — water that's too alkaline stings eyes and skin much like water that's too acidic.
How to bring pH down
- 1
Test pH and total alkalinity
They move together — read both before adding anything.
- 2
Add acid with the pump on
Muriatic acid (liquid) or sodium bisulfate (dry). Pour slowly into the deep end or a return flow, in a measured amount.
- 3
Circulate, then wait
Let it distribute and the reading settle before re-testing — give it time rather than chasing it.
- 4
Re-test and step down
Work gradually toward 7.2–7.8. Several small additions beat one overcorrection.
Muriatic acid is strong — handle it outdoors with gloves and eye protection, add acid to water (never water to acid), and never mix it with chlorine. Aquavail gives you the measured amount for your pool's volume and sequences pH with alkalinity so they don't fight.
The alkalinity connection
Total alkalinity buffers pH. If alkalinity is high, pH keeps drifting back up no matter how much acid you add — so if your pH won't stay down, bring alkalinity into the 80–120 ppm range first.
Common questions
What lowers pH in a pool — muriatic acid or dry acid?
Both work. Muriatic acid (liquid) is cheap and common for pools but harsher to handle; dry acid (sodium bisulfate) is easier and safer to store. Either lowers pH and alkalinity together — add a measured amount to circulating water and re-test toward 7.2–7.8.
Why does my pool pH keep rising?
High total alkalinity is the usual cause — it pushes pH back up. New plaster, aeration features, and salt systems can also raise it. Get alkalinity into range and pH will hold much better.
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