What should pool pH be?

7.2–7.6, ideally around 7.4 — comfortable to swim in and where chlorine works well. Below 7.2 the water is acidic and corrosive.

Why does my pool pH keep dropping?

Rain (especially acidic rain), some chlorine products, and certain sanitiser systems can pull pH down over time. Low total alkalinity also lets pH swing more easily — if pH won't stay put, alkalinity is often the underlying cause.

Soda ash (sodium carbonate), sold as pH Up, is the standard. Aeration — running jets, fountains or features — also nudges pH up gently and can help hold it.

Is low pH or high chlorine making the water sting?

Usually low pH, not high chlorine. If the water stings, test pH first — acidic water is a far more common cause than over-chlorination.

How to raise your pool's pH

Reading below 7.2? Acidic water is worth correcting quickly — it stings eyes and skin and slowly corrodes surfaces and metal fittings. Getting back into the 7.2–7.6 range is simple.

Why low pH is a problem

Below 7.2 the water turns aggressive: it's harsh on eyes and skin, and over time it corrodesplaster, grout, ladders, and heater components. Low pH is a common — and often misread — cause of stinging water; people assume “too much chlorine” when the real culprit is acidity.

How to bring it up

Raise pH with pH Up (sodium carbonate / soda ash). Add it with the pump running, let it circulate, and re-test in a few hours before adding more. As with lowering pH, small frequent corrections beat one big dose — overshooting into high pH just means reaching for pH Down next.

The amount depends on your pool volume and how far below 7.4 you are; the calculator scales it from your product's strength.

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?: 7.2–7.6, ideally around 7.4 — comfortable to swim in and where chlorine works well. Below 7.2 the water is acidic and corrosive.
Why does my pool pH keep dropping?: Rain (especially acidic rain), some chlorine products, and certain sanitiser systems can pull pH down over time. Low total alkalinity also lets pH swing more easily — if pH won't stay put, alkalinity is often the underlying cause.
What raises pool pH?: Soda ash (sodium carbonate), sold as pH Up, is the standard. Aeration — running jets, fountains or features — also nudges pH up gently and can help hold it.
Is low pH or high chlorine making the water sting?: Usually low pH, not high chlorine. If the water stings, test pH first — acidic water is a far more common cause than over-chlorination.

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 lower your pool's pH — Pool pH too high? Why it matters and how to bring it back to 7.2–7.6.
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