In this article
Clear water is not always balanced water. A sparkling pool can still sting the eyes or quietly corrode the equipment. Understanding four basic readings is enough to know what is happening in your pool and when to act.
pH
This is the most important reading because it affects everything else. The suitable range for pools is usually around 7.2 to 7.6.
- When it rises: chlorine becomes less effective, water turns cloudy and scale forms on tiles and plumbing.
- When it drops: water irritates eyes and skin and slowly corrodes metals and grout.
Free chlorine
Chlorine sanitises the water and kills bacteria and algae. The reading that matters is free chlorine, the chlorine available to sanitise. Keep a steady level within the recommended range for your sanitiser; summer heat, heavy use and dust all consume it faster.
Total alkalinity
Alkalinity acts as a buffer for pH. When it is low, pH swings quickly and is hard to control; when it is high, pH keeps drifting upward. That is why you adjust alkalinity first, then pH.
Calcium hardness
This depends largely on your local water source. Very hard water leaves white scale on tiles and inside the filter, while very soft water can etch plaster and grout. Checking it periodically protects your finishes.
The right order to balance
- Test all readings before adding anything.
- Adjust alkalinity first.
- Then adjust pH.
- Then raise chlorine to the target level.
- Run the filtration and leave time between products, and never mix chemicals together.
How often to test
- pH and chlorine: several times a week, more in summer.
- Alkalinity: every one to two weeks.
- Hardness: about monthly or after adding a lot of fresh water.
- After sandstorms or heavy use: an extra test.
Frequently asked questions
Why do my eyes sting after swimming?
Usually because of unbalanced pH or spent chlorine bound to contaminants, not because of too much chlorine.
Can I rely on test strips?
They work for daily checks, but a more accurate test now and then gives a clearer picture, especially for alkalinity and hardness.
What happens if I ignore water balance?
Algae and cloudiness appear, and grout, metals and the filter deteriorate, making repairs far more expensive than maintenance.
