When you think of acid rain, you quickly start to worry. Will its acidity cause your pool's pH to drop to the point where it needs draining? Here's what you need to know to demystify this fear.

Don't worry: even very heavy rain (50 mm, or 50 liters per square metre) only impacts 3% of the total volume of a 1.5-metre-deep pool. This dilution considerably limits the effect on overall pH.

Normal rainwater already has a slightly acidic pH, around 5.6. Rain becomes “acid” when its pH falls below 5, due to acidifying gases of human origin (industrial pollution) or natural origin (volcanoes). However, this contribution is small compared to the total volume of your pond.

More than acidity, it's what the first raindrops carry that poses the problem. Bacteria, algae spores and atmospheric pollution can find their way into your pool, disrupting water quality. After several days of rain, a shock treatment is recommended to prevent the proliferation of algae and other undesirable micro-organisms.

Water that's too acidic can be corrosive to pool surfaces and irritating to the skin. But did you know that water that's too basic can be even more problematic?

The skin's natural pH is slightly acidic, between 4 and 6. When pool water is too basic, it alters the skin's barrier function, promoting dryness, irritation, infection and microbial imbalances.

Deviating from the ideal pH (between 7.2 and 7.6) - in either direction - is harmful, both for your pool and for bathers. Regularly monitor the pH and adjust it according to rainfall to maintain a perfect balance.