What Causes Soap-Like Suds in Pool Water?

Soap-like suds on the surface of your pool can be an unsightly nuisance, the result of several things but most of all unbalanced water chemistry. Other culprits include calcium hardness, tanning lotions, sanitizing methods and use of algaecide. Use simple remedies to eliminate suds and foam in your swimming pool.


The most common reason for soap suds in your swimming pool is low calcium hardness levels. In-ground pool owners and aboveground vinyl liner pool owners who have recently cleaned the pool wall may have used too much detergent. It can be as simple as that. Runoff and deposits from the use of non-waterproof oils, lotions or sunblocks can cause the appearance of foaming and soap-like water. Other aspects of poor water chemistry such as proper sanitizing can also contribute to calcium hardness inefficiencies. The use of too much algaecide is another culprit.

Raise Calcium Hardness

Water quality can suffer when the calcium hardness falls below the normal range. Determine the levels with a testing kit or testing strips. Don't add calcium hardness increase chemicals until you are sure the levels are low; the soap-like suds may occur from other causes. Recommended calcium hardness levels fall between 180 and 220 parts per million (ppm). Depending on the test reading, add 1 lb. of calcium hardness increase for every 10,000 gallons of water to raise the raise the calcium hardness by 5 ppm. Adjust the formula in accordance with your pool's water volume and how much the calcium hardness needs to be increased.

Water Chemistry

Balance your pool's water chemistry. The addition of chlorine or other sanitizing agents can help clear the soap suds from the pool. Using a testing kit, balance the alkalinity levels first, then let the filter run for eight hours before adding other chemicals. Next, adjust the chlorine levels of your pool as indicated on the testing strips. Chlorine tablets and granulated chlorine all have different dosage recommendations based on specific product guidelines.

Other Chemicals

Pool supply retailers sell anti-foaming chemicals that can be added to your pool to reduce the appearance of soap-like suds in your pool. When used in accordance with proper water chemistry, anti-foaming agents can be effective--especially for eliminating suds from oils, tanning lotion residue or even actual soap from cleaning the pool wall. Although less likely, you will sometimes get suds in the pool even though the water chemistry is properly balanced. Anti-foam chemicals will help in these instances.