Overview
This note explains how to identify and address persistent algae problems in a swimming pool, focusing on testing and reducing phosphate levels alongside other standard treatments.
Determining the Cause of Algae
- Persistent pool algae may indicate excessive phosphates in the water.
- Verify phosphate levels before proceeding with phosphate removal.
Phosphate Testing Procedure
- Use phosphate test strips and a 10ml test tube to measure phosphate levels.
- Avoid contaminating or wetting unused strips; keep them sealed in a dry, cool place.
- Fill the test tube to the 10ml mark, insert and bend the test strip, cap the tube, and invert it slowly five times.
- Remove the strip and read the color result by looking down into the tube, matching to the provided chart.
- In the example, the pool tested showed phosphate at 300 ppb.
Phosphate Removal Treatment
- Add a phosphate-removing chemical (e.g., Phosfree) after using an algicide to kill existing algae.
- For levels at or below 300 ppb, dose approximately 16 oz per 10,000 gallons of pool water.
- For a 12,000-gallon pool, add about 16 oz (using the 4 oz cap as a measure).
- Shake the product well before dosing and pour it into the skimmer.
- Spread the dosage over a day or two to prevent filter clogging; monitor filter pressure.
- Clean the filter before starting treatment and avoid backwashing for the first week post-treatment.
Ongoing Maintenance and Results
- Weekly maintenance can use the 4 oz cap as a dosage guide.
- Effective phosphate removal, combined with algicide and maintaining high chlorine levels, prevents algae blooms.
- After one month of treatment, the pool remained algae-free and in good condition.
Recommendations / Advice
- Use algicide first to kill algae before starting phosphate treatment.
- Maintain high chlorine levels throughout the process.
- Take a pool water sample to a pool store for phosphate testing if the at-home procedure seems too complex.
- Do not backwash the filter for at least a week after dosing with phosphate remover.
Action Items
- TBD – Pool Owner: Test phosphate levels using test strips and 10ml test tube.
- TBD – Pool Owner: Clean the filter before starting phosphate removal treatment.
- TBD – Pool Owner: Add correct dosage of phosphate remover based on pool volume.
- TBD – Pool Owner: Monitor filter pressure and avoid backwashing for the first week after treatment.
- Weekly – Pool Owner: Maintain phosphate remover at recommended levels and ensure chlorine remains high.