Cloudy pool water is always a symptom of an underlying problem. Start by identifying the cause. Test pH and chlorine before adding anything.
The four most common causes
1. Water chemistry imbalance: pH above 7.8, chlorine below 1.0 mg/l, or high calcium hardness. Fix: test all parameters and correct in order â alkalinity, pH, chlorine.
2. Clogged or insufficient filter: a dirty sand filter cannot clear fine particles. Fix: backwash the filter (3 to 5 minutes), then increase filtration time to at least 12 hours per day.
3. Early-stage algae growth: greenish cloudy water indicates algae. See our article on green pool water.
4. Heavy bather load: after a party with many swimmers, the chlorine is overwhelmed by sweat, sunscreen and other organics. Fix: perform a shock treatment.
Step-by-step fix for cloudy water
- Test the water: pH, free chlorine, alkalinity
- Correct chemistry: pH 7.2 to 7.6, chlorine 1.0 to 3.0 mg/l, alkalinity 80 to 120 mg/l
- Backwash the filter
- Increase filtration time to at least 12 hours per day
- Add flocculant for persistent cloudiness (sand filters only)
- Vacuum the pool floor after flocculant settles (12 to 24 hours)
Important
Do not swim in cloudy water. Cloudy water indicates the chemistry is off. It can irritate eyes, skin and ears. Fix first, swim after.
Prevention
- Test pH and chlorine 2 to 3 times per week
- Run the pump at least 8 hours per day, 12 hours in hot weather
- Add preventive algicide weekly in warm, sunny periods
- Backwash the filter weekly
- Cover the pool when not in use
