What should pool pH be?

Aim for 7.2–7.6, with 7.4 as the sweet spot. That's where chlorine works best and the water is comfortable on eyes and skin.

Why does my pool pH keep rising?

New plaster, aeration from jets, waterfalls and fountains, and some chlorine types all nudge pH upward over time. A slow, steady climb is normal — correct it with small regular doses rather than waiting for a big swing.

How much pH Down do I add?

It depends on your pool's volume and how far above 7.4 you are. Add the amount your product's label specifies scaled to your volume, re-test after a few hours, and repeat if needed rather than overshooting.

Can I swim with high pH?

It's not dangerous in itself, but your chlorine is working at reduced strength, so the water is less protected. Bring pH back into range and confirm free chlorine is 1–3 ppm before relying on it.

How to lower your pool's pH

If your pH is reading above 7.6, it's worth fixing — high pH quietly makes your chlorine weaker and your water cloudier. Bringing it down to the 7.2–7.6 range is quick and cheap.

Why high pH is a problem

At high pH, chlorine loses much of its punch — the same reading sanitises far less effectively above 7.8 than at 7.4. High pH also encourages cloudy water and scale on surfaces and equipment. So even if chlorine looks fine on a test strip, drifting pH can leave the water dull and under-protected.

How to bring it down

Lower pH with pH Down (dry acid / sodium bisulphate) or muriatic acid. Add it with the pump running, give it time to circulate, and re-test in a few hours before adding more. Small, frequent corrections beat one big dump — overshooting into acidic water brings its own problems (stinging eyes, corrosion).

How much depends on your pool volume and how far above 7.4 you are — the calculator scales it from the strength printed on your product.

Work out your exact dose

Numbers in hand? This free calculator turns them into the exact amount for your pool's size:

pH Up & Down CalculatorHow much pH Up or pH Down your pool needs.

Frequently asked

What should pool pH be?: Aim for 7.2–7.6, with 7.4 as the sweet spot. That's where chlorine works best and the water is comfortable on eyes and skin.
Why does my pool pH keep rising?: New plaster, aeration from jets, waterfalls and fountains, and some chlorine types all nudge pH upward over time. A slow, steady climb is normal — correct it with small regular doses rather than waiting for a big swing.
How much pH Down do I add?: It depends on your pool's volume and how far above 7.4 you are. Add the amount your product's label specifies scaled to your volume, re-test after a few hours, and repeat if needed rather than overshooting.
Can I swim with high pH?: It's not dangerous in itself, but your chlorine is working at reduced strength, so the water is less protected. Bring pH back into range and confirm free chlorine is 1–3 ppm before relying on it.

More pool help

Common pool problems — Green, cloudy, low chlorine, drifting pH — what's wrong and how to fix it.
Why your pool turned green — Green water is algae from low chlorine — the step-by-step fix and how long it takes.
How much chlorine to add — Hit a safe 1–3 ppm — the rule of thumb, worked examples, and why it won't hold.
How to raise your pool's pH — Pool pH too low? Acidic water stings and corrodes — how to bring it back up.
Cloudy pool water — Clear but not green? The three usual causes and how to get back to clear.
Chlorine won't hold — Chlorine crashing to zero is a demand to shock out — how to diagnose and fix it.
How much shock to add — Reach shock level (10–15 ppm) to clear the water — what it means and how much.

Stop guessing, start swimming

Algae Later reads your pH and chlorine, tells you exactly what to add, and nudges you when it's time to test again.

Set up your pool — free