Swimming Pool Chemistry

There are five properties for swimming pool water that should be tested and adjusted.

  1. Total Chlorine/Bromine
  2. Total Alkalinity
  3. pH
  4. Total Hardness
  5. Cyanuric Acid

Tips for liquid reagent reaction and titration tests:

  • Replace testing chemicals yearly.
  • Rinse the sample tubes well with the pool water before collecting the sample.
  • Collect the test water samples 18 inches below the surface.
  • After testing empty the sample outside of the pool.
  • Rinse the sample tubes well with the pool water after emptying the sample.

Tips for using test strips:

  • Check the expiration date on the package.
  • Test strips give a lower resolution and less accuracy.
  • Dip the test strip just below the surface, dipping too deeply can wash off some of the test chemicals giving a false reading.

Warnings about adjustments:

  • Total hardness and cyanuric acid content can only be lowered by diluting the pool water! Don’t overshoot when increasing them.
  • If total alkalinity is wrong then the pH reading will bounce and be difficult to set correctly.
  • Lowering total alkalinity requires lowering the pH.
  • Total alkalinity can be raised without a major impact on pH by using baking soda (sodium bicarbonate).
  • Do not try to raise total alkalinity too quickly, the maximum recommended rate is 1 pound of baking soda per 6,000 gallons of water every 4 days.
  • When increasing total hardness divide the recommended amount by 3 and add it to the pool. Wait at least 4 hours then re-test the total hardness. Repeat this process until the test shows the desired level.

Order of chemistry adjustments:

  1. Get the chlorine on the high side. Going overboard on chlorine is never a big problem as it naturally will drop with time once you stop adding it.
  2. Adjust the total alkalinity to the minimum before working on the pH.

Tips for unusual conditions:

  • Cloudy water, chlorinate like crazy, keep it above 3ppm (5 to 10ppm is even better) for days (shocking the pool). Also leave the filter running 24/7 for these days. If shocking the heck out of the pool doesn’t clear up the water then try a pool clarifier.
  • Algae, vacuum to waste, then shock the pool like crazy with chlorine. After the algae appears to be gone the water may be cloudy from dead algae, follow the cloudy water tip above.

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