How To Balance Pool Water After A Rainstorm

pool maintenance supplies sitting next to a swimming pool

Knowing how to balance pool water is an important part of maintaining a healthy, safe swimming pool. While plenty of pool owners are pretty good at normal chemical maintenance and upkeep, a major rainstorm leaves them struggling to get their pool’s water back under control. It takes more than just a pool shock after the rain has passed. You need to understand how the rain may have affected your pool water, what that means for its levels, and how to approach the problem methodically to restore your water to perfect swimming condition.

Into Each Pool, Some Rain Must Fall

If you have an outside pool, then you’ve seen your pool water’s test levels shifts after a big storm. While a light sprinkle may barely move your chemical levels, larger rainstorms have a bigger impact that goes beyond just the volume of water introduced to your pool. It introduces contaminants that, in some cases, have spent thousands of years waiting to travel hundreds of miles to visit your backyard oasis.

dirty pool water after a rainstorm
dirty pool water after a rainstorm

You may remember from junior high science classes that clouds form from water vapor that rises from the Earth. That vapor doesn’t carry pure water but is instead water that has mixed with minerals and chemicals in the ground and plants. In the air, pollutants and chemicals can also mix with vapor. When rain falls, these chemicals are in the water, which is then introduced to your pool. While usually not in levels that are harmful to walk around in, your pool water is balanced within narrow margins to fight bacteria and algae, prevent staining and damage, and provide comfortable water to swim in. The chemicals and the volume of untreated water that carries them can disrupt this balance.

Putting Your Pool Water Back In Order

It’s no surprise that we’re a big believer in preparation. While accidental drownings cause thousands of injuries every year, the effects of poorly maintained pool water on swimmers’ health take their toll as well. If you know a big storm is expected, you can get a jump on things by adding an algaecide treatment to your pool and making sure your swimming pool safety cover is secured before the first drops fall. The cover helps prevent contamination, and the treatment helps make sure that any contaminants that do make it into the water are less likely to take hold. 

Clean And Shock

As soon as the storm passes, it’s time to get to work on restoring your pool water balance. Begin by removing any debris from your pool cover, then remove the cover. The pool should be skimmed, vacuumed, and cleaned before anything else is done. Gently scrub the sides and floor of the pool to make sure you can get rid of all contaminants. If the rain has overfilled your pool, restore it back to its normal fill line, giving you a known volume of water to work with. This can usually be done by setting your pump to backflush, attaching the flush hose, and running the pump until the water drops to the target level. 

Now you will shock your pool after the rainstorm to give it a large dose of sanitizer that will help fight any bacterial or viral threats that may have entered the system. Add the required amount to treat your pool’s volume, then allow the filter and pump to run for at least 12 hours, circulating the water and spreading the chemicals throughout. This also gives your filter a chance to catch any debris that was too small for the skimmer nets. Many pool owners choose to perform this step in the evening, allow their system to run overnight, then finish the job out in the morning.

man pouring chlorine shock into swimming pool
man pouring chlorine shock into swimming pool

Test, Balance, And Retest

With your water clean and shocked, now it’s time to balance your pool water to get it back to a swimmer-friendly condition. The rainwater has diluted your pool’s chemicals, but it also added in too much acidity for comfort. Your body is comfortable at a pH of around 7.5, which is the pH of your eyes and mucous membranes. Pure water is only a pH of 7, and the chemicals clouds pick up often lower it further. That lets us know where we need to start our testing and balancing. 

  • Alkalinity – Closely related to pH, alkalinity measures the number of carbonates in the water. Since the addition of carbonates and bicarbonates offsets the hydrogen pH measures in your pool, by adjusting alkalinity first, we’ll start to get the pH balance closer to the desired range as well. You’ll want to hit a range between 90 and 120 parts per million (ppm).
  • pH – Once we’ve reached the right alkalinity, the pH should be finetuned to between 7.3 and 7.6, depending on your general comfort level. This keeps the pool around the target of 7.5, which is great for just about every swimmer but allows you some leeway to account for your personal body chemistry.
  • Hardness – The hardness of your pool water manages how corrosive it is and how likely it is to cause scaling. Usual hardness recommendations can vary from 150 to 400 ppm, with plaster and concrete pools generally needing a higher hardness level than fiberglass or vinyl ones. A range of around 200-225 ppm hits a good sweet spot that provides a suitable pool water balance starting spot that can be adjusted as your needs dictate. 
  • Sanitizer – There are several pool sanitizer options available, and you’ll want to refer to your chosen systems direction to ensure you get enough of a sanitizer load to prevent bacterial proliferation while not over-sanitizing your swimming pool.

The Next Steps

With your pool water balanced, your pool is almost ready to get back in action, but take a few moments first to inspect your pool area for any signs of damage or hazards that may have been deposited by the storm. Clean up any trash, limbs, or other debris. Make sure your swimming pool safety fence is in good repair and that the self-closing and latching gate swings freely and latches firmly. Pool safety nets and swimming pool safety covers should be checked for rips and tears. While our ASTM-compliant pool barriers are extremely durable, Mother Nature can be fierce. 

If repairs are needed, contact your local Lifeguard on Duty installer. They’re in the neighborhood and ready to help you out. They can also help you add a cover that keeps debris out of your pool and makes balancing the pool water after a rainstorm easier. Request a free quote, and you’ll get a written estimate tailored to protecting your pool. Create a safer, healthier swimming pool with the help of Lifeguard on Duty today.

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