What Caused the Water in My Fiberglass Pool to Turn Greenish-Brown?

Mineral Levels

• If the water of the fiberglass pool is turning any shade of greenish-brown, this can indicate that there is a high level of iron or copper in the water. This can be a common problem in areas where there are copper or iron pipes, especially if the pipes in the area haven't been replaced for a while. Filling the pool with hard water can add to the buildup. Iron can also build up if there are older metal parts in the pool, such as in the filters. Improperly balanced pH can start a corrosion process that will ultimately result in the buildup of iron or copper in the water, tinting the water a distinctive greenish-brown. There are also some pool chemicals --- including algaecides --- that contain high amounts of copper and other minerals. Repeated use of these chemicals can increase the mineral levels of the pool.

Solution

• Test the pool's pH levels, and adjust as necessary. The ideal pH range should be between 7.2 and 7.6; adjusting for this will help bring the water to an alkalinity that will cause all the other chemicals added to the pool to interact efficiently. There are also chemicals called sequestering agents that can be added to the fiberglass pool to break down the minerals that are causing the discoloration. The amount of the chemical that will need to be added depends on the severity of the condition and the size of the pool.

Algae Growth

• Algae is also a possible problem if the water is turning a greenish-brown. Typically, if the problem is algae, the water will also be cloudy, and spots of algae can begin to develop. These spots will be clinging to the side and bottom of the pool. There are thousands of different types of algae, but green algae is a common offender. Present in the air and almost all types of water, it begins to multiply when there is a lack of sufficient chlorine or bromine in the pool, and can be further encouraged by several days of direct sunlight.

Solution

• Make sure that the pH of the pool is within the proper range, and test for whichever sanitizer product you've been using, whether it is chlorine or bromine. Once these readings are in the acceptable range, add algaecide to kill the algae and prevent further infection. Polyquats can be quite effective against this type of algae. In addition to adding algaecide, keep the pool's filtration system running throughout the day to remove algae from the water, and scrub free any spots that have collected on the pool floor or walls. It may also be necessary to add shock to the pool; when dealing with discolored water, this can help clear up the problem. Clean the filter several times to ensure that the algae is not just being recycled back into the pool.