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How to Treat Green Pool Water

By J. Lang Wood ; Updated September 21, 2017
Treat green pool water effectively and get back to enjoying your swimming pool.

Having a pool means hours of fun for family and friends, but swimming pools also mean that maintenance must become part of your weekly routine. Homeowners must quickly become swimming pool chemistry experts to keep their pools sanitary and sparkling. Occasionally, however, the careful balance of chemicals can go out of whack, causing a variety of problems, such as cloudy water, stains on the surfaces or colored water. When your pool water turns green, don't be dismayed.

Test the pH of your pool water to determine what chemicals will be needed to bring the water back into balance. Bring pool alkalinity, pH and calcium hardness values into normal range with the addition of muriatic acid and sodium carbonate, as recommended by the pH test.

Scrub algae from the pool's walls and floor with a pool brush.

Clean the skimmer and pump baskets to ensure that the water can run freely through the filtering system.

Run the filter continuously for 24 to 30 hours.

Backwash the filter by switching the valve.

Shock the pool water. Increase sodium hypochlorite to 10 times the normal level in one dosage. The water will turn from green to cloudy white.

Continue to brush the walls and floor to remove algae buildup.

Backwash two times daily until the water clears. Backwash by turning off the power, attaching a hose to the backwash filter and turning the power back on. Allow to backwash for two to three minutes. Rinse and turn valve and power back to normal position.

Remove the filter and rinse clean two times daily. Replace the cleaned filter.

Return the filter to normal operation when the water is clear.


Things You Will Need

  • Pool water pH test kit
  • Muriatic acid
  • Sodium carbonate
  • Pool brush
  • Sodium hypochlorite
  • Hose


  • Recommended pH for swimming pools is between 7.2 to 7.8. That range can vary a bit without causing water problems, according to BlueWaveChemicals.
  • Good filtering will help to keep a swimming pool water sparkling clean. Examine pool filters and equipment routinely to ensure proper operation.
  • Algaecides aren't needed to clean a green pool. They are mainly preventative chemicals. Keep your pool properly chlorinated and filtered and algae should not be a problem.
  • When chlorine is at 1.0 to 3.0 ppm, it is safe to swim in the water.
  • If the water is greenish-blue, the problem is too much copper precipitated out of the water. Add a metal sequestering agent to help to bring it back into solution so it can be filtered out, according to PoolManual.


  • Wear gloves and goggles when working with harsh pool chemicals, which can burn skin and eyes.
  • Keep everyone out of the pool until the water is clear and clean.