5 Things to Know About Rain and Green Pools

Rain does not turn pools green — phosphates do. Phosphates in rainwater feed algae growth, not the water itself.

Rain carries organic debris like dust, pollen, bird droppings, and lawn fertilizer runoff. All of these are loaded with phosphates and nitrates, which act as algae fertilizer.

Rain also dilutes your chlorine level. Lower chlorine means less protection against algae, so the pool can turn green within 24–48 hours.

The fix is to test phosphate levels, use a phosphate remover, and shock the pool. Most pool stores test phosphates for free.

Adding chlorine alone is not enough. Phosphates remain in the water and will continue feeding new algae, so you will burn through chlorine faster than normal.