Cloudy pool water – causes and how to clear it
Short answer: Cloudy pool water almost always comes from three things: an off-balance pH, poor or dirty filtration, and too little chlorine. Measure the pH and chlorine, adjust the pH to 7,0–7,4, flush the filter, and let it run for 24 hours. Only then add clarifier.
Why does cloudy water appear in the pool?
Turbidity is very fine particles in the water: dust, pollen, dead algae, cream residue, limescale. They are either too small for the filter to catch, or the filter has not been running long enough. The chemistry of the water determines whether the particles will clump together and be captured, or continue to float.
Cloudy pool water: what does the color indicate?
| What does water look like? | Most common reason | What to do |
|---|---|---|
| Grayish or brownish, bottom difficult to see | Dirty filter, short filtration, very fine particles | Rinse the filter, let it filter for 24 hours, then add Azuro Flokul |
| Milky white | Most often incorrect pH, sometimes hard water with a lot of limescale | Adjust pH to 7,0–7,4 with pH Minus; for limestone use Azuro CA |
| Cloudy with a greenish tint | Beginning of algae, chlorine is below 0,3 mg/l | Shock chlorination with Azuro Chlor Shock G evening and filtration 12–24 hours |
| Turbidity immediately after shock chlorination | Dead algae and sediment – this is normal | Let the filter run, then suck the sediment from the bottom |
| Cloudy after rain or after many bathers | Organic contaminants, chlorine has been used up | Measure the chlorine and perform shock chlorination if necessary. |
How to clear cloudy pool water – step by step
- Measure pH and free chlorine. The fastest way is with test stripsWithout measurement, each preparation is added blindly.
- Adjust pH to 7,0–7,4. At high pH, chlorine has almost no effect and clarifiers are ineffective. Add pH Minus or pH Plus into portions and measure again after a few hours.
- Check the chlorine. Below 0,3 mg/l it is time for a chlorinator. For cloudy or greenish water, perform a shock chlorination with Azuro Chlor Shock G: the first dose is 100 g per 10 m³ of water, best in the evening when there is no sun.
- Rinse the filter. The sand filter is backwashed until the water in the sight glass is clear. The cartridge is rinsed with a hose and, if old, replaced.
- Run the filtration for 24 hours without interruption. Don’t let the pump “rest” right now.
- If the water is still cloudy, add flocculant. It clumps fine particles into flakes: some of them are retained by the filter, while the rest settle to the bottom. Azuro Flokul (50–70 ml per 10 m³) is slowly poured into the skimmer while the filtration is running, which lasts 24 hours. Azur Bright (20–40 ml per 10 m³) also works in cooler water, and the filter should run for at least 6 hours. With both preparations, the pH should first be 7,0–7,4.
- Suck the sediment from the bottom with a vacuum cleaner and rinse the filter once more.
The most common cause is the filter
The pump should be powerful enough to pass the entire volume of the pool through the filter in about 4 hours (3 to 6 hours is acceptable). See the article for how to calculate it. Pool calculatorIf the pump is weak or only works a few hours a day in the heat, the water will become cloudy, no matter how much detergent you add.
The filter filling also ages. The stuck sand lets dirt through and needs to be replaced with a new one. quartz sand, with glass filling or with the lighter one Aquawool.
Common mistakes
- Chlorine without measured pH.
- Flocculant for green water: algae must first be removed (see how to fix green water).
- Stop filtration immediately after adding detergent.
- Too many preparations at once: then you don’t understand who did what.
Frequently asked questions
Can we swim when there is cloudy water in the pool?
Better not. When the bottom is not visible, swimming is dangerous, and turbidity usually means that the chlorine is not working properly. Wait until the water clears and the chlorine is at least 0,3 mg/l.
How long does clarification take?
Typically one to three days: about 24 hours of continuous filtration after pH and chlorine adjustment and another day or so after flocculant. If there is no change after 2–3 days, check the filter and pump.
What is the difference between Azuro Flokul and Azuro Bright?
Both are flocculants that stick together fine particles. Azuro Flokul is dosed at 50–70 ml per 10 m³ and the filtration runs for 24 hours. Azuro Bright is 20–40 ml per 10 m³, it also works in cooler water, and the filter must run for at least 6 hours.
Does flocculant help with green water?
No. In the case of green water, the cause is algae: first, the pH is adjusted and shock chlorination is performed, and flocculant is used only when the water remains only cloudy.
When to call a specialist
If after 2–3 days with the correct pH, sufficient chlorine and continuous filtration the water is still cloudy, the problem is usually in the equipment: a weak pump, a damaged filter or incorrectly connected pipes. Use our water diagnostics or call 02 996 47 55 and 0876 34 30 73.
Last content check: 30.09.2026
