Why pH matters
When pH drifts out of the 7.2–7.6 band, chlorine loses effectiveness, swimmers' eyes sting, and the pool damages itself. Low pH (acidic water) corrodes ladders, handrails, heat exchangers and pump internals, and strips grout from tiling. High pH makes water cloudy, lets scale form on tile and equipment, and weakens chlorine.
If pH is high: lower it
Use Pool Drop pH reducer, a liquid pH reducer that is a non-corrosive alternative to neat acid. Dose per 50,000 litres:
| Tested pH | Pool Drop per 50,000 L |
|---|---|
| 7.6 – 7.8 | 400 ml |
| 7.8 – 8.0 | 500 ml |
| Above 8.0 | 800 ml |
Pour along the pool edge with the filter running, keep swimmers out for one hour, then re-test.
If pH is low: raise it
Use Pool Build alkalinity increaser. It raises pH and total alkalinity together, so pH holds steady instead of swinging on every small addition. Dose per 50,000 litres:
| Tested pH | Pool Build per 50,000 L |
|---|---|
| 7.0 – 7.2 | 450 ml |
| 6.8 – 7.0 | 575 ml |
| 6.5 – 6.7 | 700 ml |
Check total alkalinity first. If it is already above about 120 ppm, stop: further additions cloud the water instead of helping.
Why home pools often go acidic
Rain, soft municipal water, and TCCA chlorine itself, which is mildly acidic and pulls pH down a little with every fortnightly dose. Owners who dose chlorine correctly all season can still watch the water turn stinging. Keeping a bottle of Pool Build next to the chlorine holds the two in balance. The Pool pH Regulator Combo packs both a reducer and an increaser, so you can correct in either direction.
Correction routine
- Test pH and total alkalinity.
- Calculate your pool volume.
- Dose the correction in one small step, not all at once.
- Wait one hour with the filter running, re-test, and correct again if needed.
Common questions
What should the pH of swimming pool water be?
Between 7.2 and 7.6. In that band chlorine works properly, swimmers' eyes don't sting and scale is not forced out of the water.
How do I lower the pH in my pool?
Use a liquid pH reducer such as Chemtex Pool Drop. Per 50,000 litres, dose 400 ml at pH 7.6 to 7.8, 500 ml at 7.8 to 8.0 and 800 ml above 8.0. Pour along the edge, keep swimmers out for an hour and re-test.
How do I raise the pH in my pool?
Use an alkalinity increaser such as Chemtex Pool Build. Per 50,000 litres, dose 450 ml at pH 7.0 to 7.2, 575 ml at 6.8 to 7.0 and 700 ml at 6.5 to 6.7.
Why does my pool pH keep dropping?
Common causes are rain, soft municipal water and TCCA chlorine, which is mildly acidic and lowers pH with each dose. Raising total alkalinity helps pH hold steady.
How long after adjusting pH can people swim?
Keep swimmers out for one hour after dosing Pool Drop or Pool Build, then re-test.
Products used in this guide
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