What to do AFTER heavy rainfall

The Effects of Heavy Rainfall on Pool Water Chemistry and How to Treat the Imbalance

Heavy rainfall can significantly impact the chemistry of your swimming pool water. Understanding these effects and knowing how to treat the imbalances is crucial for maintaining a safe and clean swimming environment. Here’s a detailed explanation of what happens and how to restore balance.

Effects of Heavy Rainfall on Pool Water Chemistry
  1. Dilution of Pool Chemicals:
    • Heavy rainfall can dilute the chemicals in your pool, including chlorine, pH, and alkalinity levels. This dilution reduces the effectiveness of sanitizers, making it easier for bacteria and algae to grow.
  2. Introduction of Contaminants:
    • Rainwater can introduce various contaminants into the pool, such as dirt, debris, leaves, and organic matter. These contaminants can affect water clarity and increase the demand for chlorine.
  3. pH and Alkalinity Imbalance:
    • Rainwater is naturally acidic with a pH around 5.0 to 5.5, which can lower the pH of your pool water. This can lead to an acidic pool environment that can corrode metal parts and irritate swimmers’ skin and eyes.
    • The total alkalinity, which acts as a buffer for pH, can also be reduced, making the pH level more susceptible to fluctuations.
  4. Temperature Changes:
    • A drop in water temperature due to heavy rain can affect the pool’s chemical balance, particularly if you use temperature-sensitive chemicals.
How to Treat the Imbalance After Heavy Rain
  1. Remove Debris:
    • Start by skimming the surface and vacuuming the bottom to remove all debris and organic matter. This prevents clogging and reduces the organic load in the pool.
  2. Test Water Chemistry:
    • Use a reliable pool test kit to measure the levels of pH, total alkalinity, chlorine, and calcium hardness.
  3. Adjust pH and Alkalinity:
    • If the pH is below 7.2, add a pH increaser (sodium carbonate/soda ash). If the pH is above 7.6, add a pH decreaser (muriatic acid).
    • For low alkalinity (below 80 ppm), add an alkalinity increaser (sodium bicarbonate/baking soda). Aim for a range of 80-120 ppm.
  4. Shock the Pool:
    • Heavy rain can introduce contaminants that increase chlorine demand. Shock the pool with a high dose of chlorine to kill any bacteria and algae. You can use a Dichlor or Trichlor granular shock, or, we recommend liquid chlorine to keep CYA in range. Follow the manufacturer’s instructions for the correct dosage based on your pool size.
  5. Balance Chlorine Levels:
    • After shocking, maintain a free chlorine level of 2-4 ppm. You may need to adjust your regular chlorine dosing schedule to maintain this level.
  6. Check and Adjust Calcium Hardness:
    • Test the calcium hardness and ensure it is within the recommended range of 200-400 ppm. If it is too low, add a calcium hardness increaser. If it is too high, you may need to partially drain and refill the pool.
  7. Run the Pump and Filter:
    • Ensure your pump and filter are running efficiently to help circulate the water and remove any remaining contaminants. Consider running the system continuously for 24-48 hours after the storm.
Preventative Measures
  • Cover the Pool:
    • If a storm is forecasted, cover your pool to prevent debris and excessive rainwater from entering.
  • Regular Maintenance:
    • Keep up with regular pool maintenance to ensure chemical levels are balanced and the pool is clean.
  • Prepare in Advance:
    • Stock up on necessary chemicals and testing supplies before the storm hits.

By understanding the impacts of heavy rain and taking appropriate actions, you can quickly restore your pool’s water chemistry and ensure it remains a safe and enjoyable place for swimming.