Cleaning A Cloudy Swimming Pool

underground swimming pool
  • 1 hours
  • Beginner
  • 0-200

A cloudy swimming pool is not an inviting sight no matter how hot the weather. Cloudy pool water is usually caused by: calcium hardness, high conditioner levels, incorrect pH, high total alkalinity, low chlorine levels, algae or filtration problems. Cloudy water is either milky white, green, or sometimes red.

Cloudy, Milky Water

swimming pool

There are four possible causes of cloudy milky looking water. Use a pool test kit to diagnose.

1. Fine hard salt particles are suspended within the water creating a milky white look. This is due to high pH or high total alkalinity, or both. Lower the pH or alkalinity using dry acid. To correct, add dry acid to a rate of one kg per 100 meters per day until readings are correct.

2. Build up of dirt and pollution due to low chlorine levels. Reverse the flow in the filter and send water out the waste line. This is referred to as backwashing the filter. Then super chlorinate the water by adding either hypochlorite or calcium hypochlorite to raise chlorine levels.

3. Effectiveness of the chlorine is reduced because of cyanuric acid build-up in the water. Cyanuric acid dilutes the effectiveness of chlorine to kill bacteria. To resolve, drain the pool water and add fresh water. This will lower the cyanuric acid levels. Then superchlorinate the pool to 10 ppm or recommended levels.

4. The filter is clogged or blocked, check for debris build-up and replace if necessary. If you are not sure how to change the filter, see your pool dealer.

Cloudy, Green Water

pool with algae

This is caused by algae build-up. The remedy is to shock-dose with chlorine such as calcium hypochlorite, sodium hypochlorite, or an algaecide. For tinted green water, super chlorinate to 10 ppm. If the water is pea soup, super chlorinate to 25 ppm. Brush off algae buildup along the pool surfaces and backwash the filter for 24 hours to remove dead algae. Any remaining haziness should be treated using a cationic clarifier.

Rust Red Water

using a pool testing kit

This is caused by ferrous metal fittings, and corroded pipes in the pool circulatory system. Chlorine oxidizes with metal creating rust. Act quickly, contact your pool dealership to see if it is safe to drain the pool. You will have to remove rust from the pool surface with a good tile and liner cleaner. Replace metal parts with PVC or copper tubing.

Prevention is always the best way to deal with pool water. The surfaces of the pool and maintenance equipment should be cleaned once a week. Add some oxidizing chemicals to the skimmer once a month to clean out the filter lines. Test the water every day or two. If you add water from the garden hose, allow the water to run for a few minutes to get contaminants out before adding water to the pool. Use a dose of shock (chlorine) and algaecide every two weeks. Pool filters should be changed every four to six weeks.