Your pool after a downpour or African dust: the steps in order

Safety first

Nobody goes in the water while there is lightning, not even when the storm seems to be moving away. Once it has passed, take a look at the plant room before you switch the power back on. If water got in, if the pump or the control panel got wet, or if the residual-current breaker tripped, do not start anything: call an electrician or your pool technician.

Also check for broken branches over the pool, a cover that has lifted and damage to the fence, especially if there are young children in the house.

What rain and dust bring into the water

Rain dilutes the chlorine and usually lowers the pH and the alkalinity. With it come leaves, soil from the surrounding surfaces, pollen and algae spores. In hot weather this combination is enough to turn the water green in one or two days.

African dust is a different matter. It is very fine: part of it settles on the floor like an orange sludge and part of it stays suspended and passes easily through the filter sand. In both cases chlorine consumption rises sharply.

The steps in order

1. Leaf net and baskets. Remove leaves and branches before they sink, and empty the skimmer baskets and the pump pre-filter.
2. Water level. If it has risen above the skimmer opening, surface skimming no longer works. Lower it using the valve's “Waste” position or with a pump. In an overflow pool, check that the balance tank is not overflowing.
3. Continuous circulation. Let the pump run non-stop for about 24 hours.
4. Brushing. Brush the walls and floor so the dust does not stick and can be picked up by the filter.
5. Vacuuming. Once the sediment has settled, vacuum slowly. If there is a lot of it, vacuum on “Waste” so the filter does not clog, then top up the water.
6. Test and correct. First alkalinity and pH (7.2–7.6), then chlorine. After a heavy storm or a lot of dust you will usually need shock chlorination, always with the chlorine dissolved first and never as granules sitting on the liner.
7. Filter. Backwash when the pressure rises, probably more than once over the following days.

If the water stays cloudy or turns green

The very fine dust particles often need help. A clarifier binds them into larger ones so the sand can hold them. A flocculant makes them settle on the floor so you can vacuum them straight to waste. Follow the product instructions and do not combine products without a reason. More detail in our guide to cloudy water.

If the water has taken on a green tint, the priorities change: brushing, shock and continuous filtration, as we describe in green pool water.

Prevention next time

• When the forecast shows dust or a storm, put the cover on, as long as it can be secured well enough for the expected wind.
• Raise the chlorine towards the upper end of the 1–3 mg/l range before the bad weather.
• Keep gutters and floor falls clear so that water from the yard does not end up in the pool.
• Tie down or put away umbrellas, cushions and light furniture so they do not end up in the water.

Questions

See also