Why Is the Plastic in My Pool Yellowing?

Algae Growth

• If the plastic in the swimming pool is beginning to turn yellow, it could be a sign that mustard algae is beginning to gain a foothold in the pool. If the discoloration can be wiped away with some scrubbing but quickly reappears, the problem is most likely a chemical imbalance that has given algae room to grow. Mustard algae, commonly found in the shady areas of the pool, can multiply quickly and be extremely resistant to different kinds of algaecides. Most easily seen on the white plastic parts of the pool it will also be visible on the walls and sides of the pool. Once mustard algae begins to grow, getting it under control can be a season-long battle.

Algae Treatment

• Maintain a high level of chlorine or bromine in the pool; mustard algae will be extremely resistant to normal levels, especially once the microorganisms begin to multiply. The application of algaecides will also help control infection, but select an algaecide that is specifically formulated for yellow or mustard algae, as this type is resistant to algaecides geared toward ridding pools of other, more vulnerable types of algae. In order to remove the discoloration from the plastic parts of the pool, scrub carefully with a stiff brush. This releases algae organisms into the water, where they can be removed by the filter.

Mineral Staining

• The buildup of minerals in the pool water can also be the cause of yellow discoloration on the pool's plastic parts. A buildup of iron or copper is a common cause for discoloration, and can usually be attributed to the use of well water that has not been properly treated, or the presence of old equipment that is beginning to corrode and release minerals into the water. If mineral buildup is the problem, the yellow discoloration will be difficult to remove. If left untreated for a long period of time, the discoloration can become stains that will remain even after the excess minerals have been removed from the water.

Balancing Minerals

• In pools that rely on well water or city water that has a high iron or calcium content, it may be necessary to install a pool filtration system designed specifically to remove metals and minerals from the water. Sequestering agents can also be added to get rid of the minerals. For pools that have regular problems with the appearance of algae, the repeat use of algaecides can result in the buildup of copper and other minerals; if this is the case, using a sequestering agent along with the algaecide can help prevent problems before they happen. The problem could also be nearby and frequent applications of fertilizer; sequestering agents can also be used to get rid of the granules that make their way into the pool. If mineral problems are caught and corrected quickly, many times the plastic can be scrubbed clean before the discoloration is permanent.