pH is the reading that decides whether everything else in the pool works. Chlorine at the right level does almost nothing if pH has drifted high.
Here is the target, and how to adjust pool pH safely in a South African pool.
What Should Pool pH Be?
Target 7.2 to 7.6, with 7.4 the ideal.
That band is not arbitrary. It is where chlorine stays active and where the water is comfortable on skin and eyes.
Why Pool pH Balance Controls Everything Else
At pH 7.0 chlorine is roughly 75% active. At pH 8.0 it is around 20% active.
The same chlorine dose does a fraction of the work. People respond by adding more chlorine when the real fix costs a cup of acid.
- High pH: cloudy water, scale, chlorine stops working, eyes sting
- Low pH: corroded fittings, etched marbelite, faded liners, itchy skin
How to Lower Pool pH
Use hydrochloric acid, sold locally as pool acid, or dry acid (sodium bisulphate).
As a working guide, about 100 ml of 33% pool acid per 10,000 litres drops pH by roughly 0.1 to 0.2, depending on alkalinity.
- Pour acid slowly into the deep end with the pump running
- Never pour acid into the skimmer
- Always add acid to water, never water to acid
- Wait four to six hours, then retest before dosing again
Alkalinity acts as a brake. If total alkalinity is high, pH will resist moving, and that is a sign to fix alkalinity first.
How to Raise Pool pH
Soda ash (sodium carbonate) raises pH with little effect on alkalinity. Baking soda raises alkalinity and nudges pH up with it.
Aeration also raises pH with no chemical at all. Running a water feature or pointing the return jets upward will lift pH over a day or two.
Pool pH Keeps Rising: Why It Happens in Cape Town
A pH that climbs every few days is normal here, and there is usually a specific cause.
- Salt chlorinators push pH up continuously as a by-product
- Wind-driven aeration, which Cape Town has plenty of, raises pH
- Water features and fountains do the same
- Fresh marbelite leaches lime for the first few months after a reline
- Total alkalinity sitting above 120 ppm drags pH up with it
If you are tired of dosing acid weekly, borate buffering holds pH far more steadily. Our pool borate guide explains it.
Pool pH Testing: Get an Accurate Reading First
Test strips fade. A strip tub opened last summer will read wrong, and you will dose against a number that is not real.
Use a liquid test kit or a fresh strip tub, test at elbow depth away from the returns, and always test pH and alkalinity together.
Order of Adjustment: Pool pH and Alkalinity
Always correct total alkalinity first, then pH. pH will not hold while alkalinity is out of range.
Our pool alkalinity guide has the dosing tables in litres.
Pool pH Will Not Hold? Get It Tested in Cape Town
A pH that moves every few days points to alkalinity, a chlorinator or a fresh surface, not bad luck.
Our team tests and balances pool water across Cape Town and the Winelands. We work from a real reading, not a guess. Request a free quote or see our pool maintenance services.
