Why is my pool green (and how to fix it fast)
A green pool is almost always an algae bloom caused by too little chlorine. The fix is a big, sustained dose of chlorine — shock to the right level and hold it there — plus good circulation and filtering. Most pools clear in 1–3 days.
Step by step
- Test and lower pH firstBring pH down to about 7.2 so chlorine works at full strength, and note your CYA — it sets how much chlorine you’ll need.
- Shock to ~40% of your CYARaise free chlorine to shock level (e.g. CYA 40 → about 16 ppm) and hold it. Use our shock calculator for the exact amount.
- Brush and run the pump 24/7Brush walls and floor daily and keep the filter running continuously to clear dead algae.
- Re-test and re-dose every few hoursChlorine gets consumed fast fighting algae. Top it back up to shock level until it holds overnight.
- Confirm it’s clearWhen overnight free-chlorine loss is under 1 ppm, the water is clear, and combined chlorine is below 0.5 ppm, you’re done. Let chlorine drift back to normal before swimming.
FAQ
How long does it take to clear a green pool?
Usually 1–3 days if you hold shock level, brush, and keep the filter running continuously. Severe blooms take longer.
Can I swim in a green pool?
No — wait until it’s clear and free chlorine has returned to the normal 1–3 ppm range.
Related
Stop guessing — get the exact fix
DoseMyPool turns your test numbers into the precise doses and the safe order to add them. Free on the App Store.