Swimming Pool Rain

Coping With Rain

With summer in full swing, it’s time for BBQ’s, outdoor events, long nights, and days spent with friends and family in your in-ground swimming pool. It’s also time for summer rain storms. In northwest Ohio and Southeast Michigan as the humidity builds, so does the possibility of rain. Often times it comes fast, hard, and in copious amounts. You may think that coping with rain is just the normal part of summer, but rain can have adverse effects on your swimming pool.

It may come as a surprise, but the problems caused by rain do not result from dilution of the chemicals in your pool water. An inch of rainwater added to a typical 20,000-gallon pool (about 670 sq. ft. of surface area) increases the amount of water by roughly 2%, Therefore, dilution isn’t an issue.

The issue of rain water and your pool causing a potential problem comes from the hard, full rains, or an all-day storm dumping 1-3 inches. Rain is acidic. It has a lower pH (potential hydrogen) level than what we recommend is a good level for your pool. We advise between 7.4 and 7.6. The reason for this number is that the human eye has a pH of 7.5. Major fluctuations from this can cause serious discomfort. You’ve heard it plenty of times the ‘my eyes are burning’ or ‘the chlorine is too high’ from a child or an adult. Very rarely is chlorine an issue if your eyes are feeling uncomfortable while in the pool. It’s more likely that the pH is low, or acidic. Normal rainwater has a pH of about 5.0. Therefore, depending on how much rainfall you received, it can lower the pH of the pool.

In this case, you may need to drain the pool a few inches and re-test the chemicals. The pH will have lowered, and the chlorine may be slightly diluted.

You don’t always need to raise the pH every time it rains. A light rainfall of .25 – .50 inches may temporarily lower the pH in the pool, but not by much and will recover on its own. If you always maintain proper water chemistry, especially the pH, alkalinity and stabilizer, a bit of rain in the pool is nothing to worry about.

There are some advantages to getting rain in your pool. There are certain chemicals levels that cannot be lowered without diluting the water. These are your stabilizer and calcium. Basically, if you use chlorine tablets, they have stabilizer in them and over time, can over stabilize the pool water and will need to be diluted. Also, if the calcium levels are high, rainfall can help dilute that, too.

Coping with rain in your pool is a necessity and making sure your area is safe is also necessary. If you know that a storm is coming, you can be prepared for it, and minimize potential damage.

  • Shut off the power to your pump
  • Cover your pump and filter
  • Store or secure your patio furniture
  • Ensure that your pool toys and accessories are put away

Then it’s time for the cleanup.

Remove any debris from your pool, skimmer and pump baskets before starting your pump again. It may also be necessary to brush and vacuum your pool as well. Coping with rain is a fact of life when you have an in-ground swimming pool. Knowing how to properly handle it will keep get you back in your pool in no time.


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