Green pool water: how to fix it

Why pool water turns green and the step-by-step to get it blue again: brush, fix the pH, shock with chlorine and filter.

2 min read

Green water is algae. It appears when chlorine stays low for a few days, especially in hot weather or after rain. The good news: you can almost always fix it without emptying the pool.

Step by step

1. Scoop out leaves and large debris.

2. Brush the walls and floor thoroughly. Brushing loosens the algae so the chlorine can reach it.

3. If you have a kit, bring the pH to about 7.2 to 7.4 before adding chlorine. At high pH, shocking works poorly.

4. Add a shock dose of chlorine (superchlorination) and run the filter for 24 hours.

5. If it's still green the next day, repeat the same dose.

6. Once the water clears, vacuum the dirt that settled on the floor and clean the filter.

Nobody in the pool during treatment. Only swim once the water is clear and chlorine is back to 3 ppm or less, which usually takes 24 to 48 hours.

Common mistakes

• Adding chlorine without brushing: algae stuck to the walls survives and the water turns green again.
• Turning the filter off too soon: dead algae stays floating and the water goes cloudy.
• Mixing products in the same bucket: besides being dangerous, one cancels out the other.

Green water that turns cloudy after a shock means the treatment worked: now it's time to filter and vacuum.