Pool maintenance in hot weather: a practical checklist

Short answer: in hot weather your pool uses more disinfectant and the water changes faster. So test more often — at least before swimming and after busy hours; keep skimmers, filter and walls clean; base pump run time on your equipment and use rather than on a fixed number; and check again after a busy day, a thunderstorm or heavy rain.

Why hot weather changes your water

• Sun: sunlight breaks down chlorine, especially when there is no stabiliser in the water.

• More swimmers: sweat, sunscreen, skin cells and other organic material use up disinfectant.

• Warmer water: algae and other micro-organisms can develop faster in warm water if disinfection falls short.

• Dirt from outside: wind, dust, pollen, leaves and insects end up in the water and the skimmer.

• Summer showers: rain dilutes the water and washes in dirt, which can affect pH and disinfection.

The result: a routine that worked fine in spring may not be enough during a hot week.

Checklist before a hot spell

• Check that your test strips or test kit are within their expiry date and that you have enough.

• Clean or backwash the filter following the manual, so you start with a clean filter.

• Empty the skimmer and pump baskets and check that the pump primes properly.

• Make sure you know your water volume; you need it to dose products according to the label.

• Store your products cool, dry, closed and out of reach of children. Heat and moisture can affect products.

Checklist for every hot day

1. Test before swimming: pH and free chlorine. The CDC advises home pool owners to check at least twice a day, and more often during heavy use.

2. Compare with the recommended range for your type of disinfection. For home pools the CDC lists a pH of 7.0 to 7.8 and at least 1 ppm (mg/l) free chlorine (2 ppm when using stabiliser).

3. Correct only what is needed, one product at a time, following the label.

4. Empty the skimmer baskets if there are leaves or insects in them.

5. Have swimmers take a quick shower before getting in; less sweat and sunscreen in the water means lower demand.

After a busy day

• Test again at the end of the day or the next morning; after many swimmers, demand is often much higher.

• Look at clarity and smell, but judge the water on the basis of the test.

• Check the skimmer and filter; after a busy day there is often more dirt in them.

• Write down what you measure. If you see the same pattern after every busy day, you can adjust your routine to it.

After a thunderstorm or heavy rain

• Remove leaves and debris as soon as possible.

• Test pH and free chlorine again: rain can affect both.

• Check the water level relative to the skimmer, so the skimmer keeps working properly.

How long should the pump run?

There is no number that's right for every pool. The filtration time you need depends on the water volume, the capacity of pump and filter, the type of pump, the temperature and the number of swimmers. Start with your equipment manual and watch the signs: if the water turns cloudy faster in hot weather or chlorine drops quickly, discuss with your installer or a pool professional whether your filtration schedule suits summer conditions.

Weekly in summer

• Brush walls, steps and corners.

• Check and clean the filter following the manual.

• Check the stabiliser level if you use stabilised chlorine and your test supports it.

• See whether you have enough products and test strips, and whether packaging is properly closed.

Read more about the link between pH and disinfection in pool pH and chlorine: why you should measure both. And if the water turns green anyway, follow this order before you add products.

Frequently asked questions

Should I test more often than usual in hot weather?

Yes. The CDC already advises at least two tests a day for home pools and hot tubs, and more during heavy use. On hot, busy days an extra test after swimming is sensible.

Can I just add a fixed extra amount of chlorine when it's hot?

Preferably not without testing. The extra demand differs per day and per pool. Test, compare with the range and dose according to the label and your water volume.