Cloudy water is the pool telling you something is out of balance. The fix depends on the cause, so start by working through these five possibilities in order.
1. Low or used-up chlorine
If free chlorine is near zero, organic matter is building up. Shock the pool and keep the pump running.
2. High pH or alkalinity
High pH makes calcium fall out of solution and turns water milky. Lower alkalinity first, then pH.
3. A dirty or worn filter
Check the pressure gauge. A reading 8–10 psi above clean means it is time for a deep clean.
4. Not enough run time
In summer most pools need eight to twelve hours of filtration a day.
5. Early algae
A dull, hazy look before water turns green is often the first sign of algae. Brush hard, shock and clean the filter within the same day.
