What a storm actually does
Rain dilutes everything: chlorine, cyanuric acid, calcium, alkalinity. A pool that was perfectly balanced is suddenly under-protected right when organic load spikes.
Wind adds leaves, dirt, and sometimes roof grit. Runoff from the yard brings in phosphates and organics that feed algae. And in a real downpour, the water level can rise past the skimmer, which stops surface skimming entirely.
The first day
Get the big debris out before it sinks and stains. Leaves and organic matter left on plaster overnight leave marks that outlast the storm.
Empty the skimmer and pump baskets — they will be full, and a clogged basket starves the pump. Check the cleaner too; storm debris is what tears cleaner bags.
Lower the water back to mid-skimmer if it's overtopped, and run the filter longer than usual to clear the cloudiness.
The chemistry that gets missed
Chlorine goes first and it goes fast. Testing and restoring sanitizer within a day is the single thing that keeps a storm from turning into a green pool.
But diluted cyanuric acid means whatever chlorine you add is unprotected against sun, and diluted calcium and alkalinity push LSI negative. Adding chlorine alone treats the symptom; the full set of readings tells you what actually changed.
Brushing after a storm matters more than usual, because the fine silt that settles is exactly where algae takes hold.
When it's already too far gone
If the pool has been sitting cloudy or green for several days, it's past a cleanup and into recovery work — filtration, staged treatment, and sometimes replacing water if cyanuric acid or debris load makes clearing it impractical.
The judgment call there is honest math: clearing a badly turned pool can cost more in chemicals and time than draining and refilling it. That's the conversation, not an upsell.
