Your pool after a storm: the right moves, in order
- A storm delivers everything at once: debris, dust, acidic diluting rain — and often water that turns within 48 hours.
- The right order: clean (net, skimmers) → filter at length → test → correct.
- Dose NOTHING before testing: the rain has shifted pH, alkalinity and sanitiser in unpredictable proportions.
- After a big summer storm, a well-dosed preventive shock often heads off the green water two days later.
A good summer storm puts your pool through the equivalent of a week of mistreatment in a single hour: debris (leaves, twigs), dust and pollen washed out of the air — a feast for algae — and rain that’s often slightly acidic, diluting the sanitiser and shifting the pH. The frequent result: water that turns green 24 to 48 hours later, just in time for the sun to come back. The right moves, in order: clean, filter, test, correct — and above all, dose nothing blind: after a storm, you no longer know your water until you’ve measured it.
What the storm actually did to your water
Three simultaneous assaults. The organic and mineral load: everything the wind and rain picked up ends in the pool — nutrients included, exactly what algae crave. Dilution: tens of millimetres of rain mean hundreds, even thousands, of litres of fresh untreated water, lowering the sanitiser concentration accordingly. Imbalance: rain, slightly acidic and very soft, pulls the pH and alkalinity down — sometimes noticeably after a big downpour.
And all of this usually lands on warm water, where biology moves fast. The countdown has started.
The right moves, in order
1. Clean what floats, empty the baskets. Net the surface, empty the skimmers and pump basket: stewing debris is a nutrient dispenser. If the level rose too much (drowned skimmers), drain the excess.
2. Brush if the storm made a mess. Dust and soil deposited on the walls will end up in the water anyway: better to send them to the filter right away.
3. Long filtration. Several hours of continuous filtration at minimum — time to mix in what the storm delivered and capture the particles.
4. Test — this is the key moment. pH, sanitiser, and ideally alkalinity. Thirty seconds of test-strip photo, and you know exactly where the storm left you.
5. Correct in order: pH first, sanitiser second. The amounts depend on what the test reveals and on your volume — it’s a textbook case for calculated dosing, because the post-storm state is unpredictable by definition.
6. The preventive shock, case by case. Big storm + warm water + a pool that was already borderline beforehand: a well-dosed shock now costs far less than Saturday’s green water. The app recommends it (or not) based on your actual readings.
The days that follow
Keep an eye on the water for 48-72 hours: that’s the window in which “shaken” water tips over. A slight haze settling in, walls turning slippery, pale green in the corners → act immediately — it’s ten times easier now than three days later. The app schedules a follow-up re-test after the storm and watches the trend — and the storm becomes a non-event.
Frequently asked questions
Should you always chlorinate after a storm?
No — not before testing. The rain has shifted pH and sanitiser unpredictably: dosing blind means correcting a state you don't know. Test first (30 seconds), then treat, in the right proportions.
Why does the water often turn 1 to 2 days after the storm?
The storm delivered nutrients (dust, pollen, debris) and diluted the sanitiser, often into warm summer water: the perfect cocktail for algae. Hence the immediate test and a quick response.
Should I lower the water level if the rain raised it?
Yes, if the water sits above the top of the skimmers: they skim poorly when drowned. Drain the excess to get back to a mid-skimmer level.
Is lightning a risk for the pool?
During the storm, yes: never swim during a thunderstorm (water conducts electricity). As for the equipment, the installation's electrical protections do the job.