Cloudy or milky pool water: why, and how to fix it
Cloudy, whitish or “milky” pool water is usually caused by microscopic particles in suspension that the filter can’t retain: dust, fines, sunscreen residue, precipitated calcium or excess chlorine. The standard fix is: check the pH (target 7.2–7.6), add a flocculant or clarifier, let it settle for 6–12 h and vacuum the bottom. The water is crystal-clear in under 24 h.
Paso a paso
- 1
Rule out green water and measure chlorine/pH
If the water has a green tint, it’s algae (see the green-water guide). If it’s white/cloudy/greyish with no green tint, it’s particles in suspension. Measure chlorine and pH before going on.
- 2
Clean the filter
Backwash the sand filter for 2–3 minutes until the water runs clear through the sight glass. A saturated filter won’t retain fine particles.
- 3
Apply flocculant
50–100 ml of liquid flocculant per 25 m³, poured around the pool with the pump running. Then STOP the pump — the flocculant needs still water so the particles clump together and settle to the bottom.
- 4
Wait 6–12 h with the pump off
The clumped particles will settle to the bottom, forming visible sediment. The longer you leave it (ideally overnight), the clearer the water above.
- 5
Vacuum the sediment off the bottom
Vacuum with the manual cleaner in “waste” mode if your skimmer allows it — that way the sediment goes straight to the drain without clogging the filter. If not, vacuum normally and backwash when you’re done.
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Flocculant or clarifier: which should I use?▾
Flocculant (liquid or tablets) is more aggressive; it groups particles together and makes them sink within hours. Clarifier is gentler; it improves filtration but doesn’t remove sediment. For very cloudy water: flocculant. For preventive maintenance: clarifier.
How much flocculant should I add?▾
As a treatment dose: 50–100 ml of liquid flocculant per 25 m³. As weekly prevention: 25–50 ml per 25 m³.
Why is the water still cloudy after adding flocculant?▾
Three common causes: (1) the pump was running (it must be off to let the sediment settle), (2) the dose was insufficient, (3) the filter is saturated and re-suspends the particles. For (2) and (3): repeat the treatment and clean the filter.
Sigue leyendo
Green pool water? How to clear it up in 24–48 hours
Green water = algae. Shock chlorine + algaecide + flocculant, in the right order. Results in 24–48 h.
Spring pool start-up: step by step
Remove the cover, top up the level, shock chlorine, algaecide, flocculant, adjust the pH and filter for 24 h. Ready in 48 h.