You don't need to be a chemist to keep a pool clear. Five numbers tell you almost everything. Test at least once a week in season, and more often in hot weather or after a party.
1. Free chlorine
This is what kills algae and germs. Too low and the water turns cloudy or green. Keep it steady rather than letting it swing between zero and very high.
2. pH
pH tells you how acidic the water is. Around 7.2 to 7.6 is comfortable for swimmers and lets chlorine work. High pH makes chlorine weak and can cloud the water; low pH irritates eyes and is hard on equipment.
3. Total alkalinity
Alkalinity keeps pH from bouncing around. If your pH won't hold still, fix alkalinity first.
4. Calcium hardness
Water that's too soft can be hard on surfaces and equipment; too hard and you get scale. Fiberglass pools are forgiving here, but it still matters for heaters and salt cells.
5. Stabilizer (cyanuric acid)
Stabilizer protects chlorine from being burned off by the sun. Too little and chlorine disappears by afternoon. Too much and chlorine stops working well, and the only fix is replacing some water.
The order to fix things
- Alkalinity first
- Then pH
- Then chlorine
- Calcium and stabilizer as needed
Simple habits that prevent most problems
- Test weekly and write the numbers down
- Run the pump long enough every day
- Shock after heavy use or big storms
- Keep the filter clean
Rather not deal with chemicals? We handle it every week.
See maintenance plans