How to Adjust Phosphate Levels in Pools

Purchase a phosphate testing kit and phosphate decreasing chemicals that use aluminum and lanthanum compounds to eradicate the phosphate. Both the test kits and chemicals can be purchased at a pool supply store, but remember that a standard pool-water test kit won't check for phosphates.

Shock your pool water to quickly elevate the amount of sanitizer which can lower phosphate levels. A sanitized pool can limit the amount of phosphates in the water. Dilute granular shock and add at the rate of 1 lb. for every 10,000 gallons of water. Adjust as necessary to fit your pool's capacity. Run the filter for 24 hours.

Test the water with the phosphate test kit. Proper phosphate levels should be at or below 125 parts per billion. Add the phosphate-decreasing chemicals through the pool skimmer at a rate that corresponds with your water capacity. Consult the chemical guidelines, as the dosage varies based on gallons and phosphate concentration of the water.

Run the filter consecutively for 24 hours. Re-test the water and adjust as necessary after 36 hours.