Green pool water? How to clear it up in 24–48 hours
If your pool water is green, it’s because there are algae. The standard fix is four steps in this order: adjust the pH to 7.2–7.6, apply shock chlorine (15–20 g/m³), add an algaecide and, the next day, a flocculant so the particles settle to the bottom and the pool vacuum can collect them. Within 24–48 h the water is crystal-clear again.
Paso a paso
- 1
Adjust the pH to 7.2–7.6
Measure it with a pH test. If it’s high (>7.6) add pH reducer; if it’s low (<7.2) add pH increaser. Until the pH is in range, the chlorine won’t work properly.
- 2
Apply shock chlorine (shock treatment)
Dissolve 15–20 g of shock chlorine per m³ of water in a bucket and pour it around the edge of the pool with the pump running. Treat at night so the sun doesn’t break the chlorine down.
- 3
Add an algaecide
8–12 hours after the shock chlorine, pour in a multi-purpose algaecide (200 ml per 25 m³ as a shock dose) spread around the pool. Keep the pump running for 24 h.
- 4
Flocculant the next day
Once the water turns from green to cloudy/greyish-white, add flocculant (50–100 ml per 25 m³) so the particles settle to the bottom within 6–12 h.
- 5
Vacuum the bottom
Once the bottom is covered in sediment, vacuum it slowly with a manual pool cleaner or robot. Clean the filter when you’re done.
- 6
Keep free chlorine at 1–3 ppm
Once the water is back, check chlorine and pH every 2–3 days. Keep free chlorine at 1–3 ppm using tablets in the dispenser, and do a weekly preventive treatment with algaecide.
Productos recomendados
Los mismos que te llevarías de nuestra tienda física en La Cañada (Paterna).
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Why has my pool turned green?▾
Algae grow when free chlorine drops below 1 ppm or the pH gets out of control. Common causes: rain, extreme heat, heavy use, or the chlorine dispenser running empty without you noticing.
How long does it take to clear green water?▾
With shock chlorine + algaecide + flocculant, usually between 24 and 48 hours. Very advanced green pools can take 3–4 days and need two rounds of treatment.
Do I need to empty the pool?▾
No, almost never. Draining the water is usually the last resort, and only if the chemicals don’t work or there’s a structural problem. Before draining, ask us on WhatsApp; in 95% of cases the water recovers with product.
Can I swim after the treatment?▾
Wait until free chlorine is between 1 and 3 ppm (measurable with a chlorine test). After shock chlorine it usually takes 24–48 h to return to safe levels.
Sigue leyendo
How much chlorine to add to a pool? Dose table per m³
Maintenance: 200–250 g/25 m³ per week in tablets. Shock: 15–20 g/m³. Target free chlorine: 1–3 ppm.
Cloudy or milky pool water: why, and how to fix it
Cloudy ≠ green. Cause: particles in suspension (fines, calcium, debris). Fix: flocculant + intensive filtration.
Types of pool chlorine: tablets, granular and shock compared
Tablets (maintenance) · Granular (quick adjustment) · Shock (emergency). Three uses, three products.