The ideal pH for your pool is 7.2 to 7.6. Outside this range, chlorine loses effectiveness and the water can irritate eyes and skin. Test 2 to 3 times per week and correct immediately if the value falls outside this range.
Why does pH matter so much?
pH determines how effective your chlorine is. At pH 7.0, about 73% of chlorine is active. At pH 8.0, only 21% is active. You can add the right amount of chlorine, but if the pH is too high, it does almost nothing.
The pH also affects your body and your pool:
- pH too low (below 7.2): eyes and skin irritate quickly, metal components corrode faster, swimwear wears out sooner
- pH too high (above 7.6): chlorine loses effectiveness, calcium scaling on walls and equipment, cloudy water
Human eye fluid has a pH of 7.4. Keeping your pool pH around that value means literally comfortable swimming.
Ideal pH values
| Value | Assessment |
|---|---|
| Below 7.0 | Too low, corrosive, irritating |
| 7.0 to 7.2 | Slightly low, chlorine works well but may irritate |
| 7.2 to 7.6 | Ideal range |
| 7.6 to 8.0 | Too high, chlorine loses effectiveness |
| Above 8.0 | Far too high, barely any disinfection |
How to measure pool pH
Test strips: dip a dry strip 30 cm deep for 1 second, hold horizontal and compare after exactly 15 seconds. Good for daily checks.
Digital pH tester: accurate to 0.01. Calibrate every 2 to 4 weeks with a pH 7.0 buffer solution. Best for serious pool maintenance.
Tip
Always take your water sample at 30 to 40 cm depth, at least 30 cm from the wall. Surface water gives a distorted reading due to evaporation.
pH too low: what to do
Use pH increaser (sodium carbonate). Add 10 grams per 10,000 litres to raise pH by approximately 0.1. Always dissolve in a bucket of water first, then pour gently around the pool perimeter. Run the pump for 4 hours and retest.
pH too high: what to do
Use pH decreaser (sodium bisulfate). Add 10 grams per 10,000 litres to lower pH by approximately 0.1. Always dissolve in water first. Wear gloves and eye protection. Run the pump for 4 hours and retest.
Warning
Never pour pH decreaser or increaser directly onto pool surfaces, steps or liners. Always dissolve in water first to prevent damage.
How much chlorine do you need at different pH levels?
| pH | Active chlorine | Dose needed for same effect |
|---|---|---|
| 7.2 | 63% | 1.2x |
| 7.4 | 48% | 1.5x |
| 7.6 | 33% | 2.2x |
| 8.0 | 21% | 3.5x |
At pH 8.0 you need 3.5 times more chlorine than at pH 7.0 for the same disinfecting effect. Good pH management directly reduces your chlorine costs.
