Why Is My Pool Green? A Quick Diagnosis

Green water means algae is growing, which usually happens when free chlorine is too low to keep up. Heat, rain, heavy use, and poor circulation all make it more likely.

Start by testing the water. High pH makes chlorine less effective, and high stabilizer (CYA) can slow its killing power. Fix pH first, then brush every surface, clean the filter, and run the pump continuously while you shock the pool.

Retest and repeat until the water is clear and the chlorine level holds steady. Then find the cause, whether it was low chlorine, short pump run time, or a dirty filter, so it does not come back.