Cloudy Pool Water: 7 Causes and How to Fix Each One

Cloudy pool water isn't algae (yet) — but it's often the last warning before algae takes over. Here are the seven real causes of cloudiness and how to fix each one.

1. Chemistry imbalance

The most common cause. Usually one or more of:

• High pH (over 7.8) — calcium precipitates and clouds water
• High calcium hardness (over 450 ppm) — same mechanism
• High total alkalinity (over 120 ppm) — causes chemistry to “lock” high
• Low free chlorine (under 1 ppm) — organic matter isn't being killed

Fix: Balance chemistry before adding anything else.

2. Filter failure

Cloudy water that doesn't clear within 24 hours of running the filter means the filter isn't working:

• DE grids torn — water bypasses filtration
• Cartridge filter overdue for cleaning (every 6 months in South Florida)
• Sand filter channeling (sand over 5–7 years old)

3. Early algae bloom

Before a pool turns green, it often turns milky or cloudy white. If chemistry looks right but clarity is dropping, shock to 10 ppm and run the filter 24/7.

4. Fine dust / pollen / pollutants

South Florida's pollen season (Feb–May) and construction dust from nearby projects can overwhelm even a good filter. Use a clarifier to bind particles into filter-catchable clumps.

5. Total dissolved solids (TDS)

TDS over 2,500 ppm causes cloudy water that no amount of chlorine fixes. Test TDS annually. If high, partial drain (30–50% water exchange) resolves it.

6. Phosphate overload

Phosphates over 1,000 ppb can cloud water even without visible algae. More on phosphates in South Florida pools.

7. Pump not running enough

Minimum 8 hours/day in summer, 6 hours in winter. A clean filter with a weak pump schedule still leaves water cloudy.

When to call a pro

If you've adjusted chemistry and cleaned the filter and the pool stays cloudy for 3+ days, the filter is likely damaged (DE grids, torn cartridges, or channeling sand). Request a diagnostic.

Frequently Asked Questions