Fiberglass Pool Chemical Levels

Disinfectant Levels

• Because a fiberglass swimming pool has non-porous pool basin surfaces, pool algae growth is inhibited. Accordingly, only 1 to 3 parts per million (ppm) of chlorine is needed in a fiberglass swimming pool. Bromine can also be used to disinfect a fiberglass pool's water, and 2 to 4 ppm is recommended. Swimming pool water disinfectant levels are needed to prevent general bacterial and organic matter contamination. Fiberglass pools also require lower chemical disinfectant levels because their surfaces are easy to manually clean.

Pool pH

• The pH level of a swimming pool's water is really the most important component of its water chemistry. If swimming pool pH is too low or too high, pool disinfectants work sluggishly or not at all, in the case of chlorine. A fiberglass swimming pool should have an ideal pH level of 7.4 to 7.6. The low-maintenance character of a fiberglass pool's basin makes it a bit easier to maintain proper pH levels using smaller amounts of pH-balancing chemicals.

Total Alkalinity

• The total alkalinity of a swimming pool's water is related to the pH level in that water but alkalinity and pH are separate factors nonetheless. Pool total alkalinity will tell you how well your pool's water will resist changes to its pH. A fiberglass swimming pool's total alkalinity level should be between 80 and 150 ppm. Total alkalinity in a pool is raised using sodium bicarbonate (baking soda) and lowered with either muriatic acid or sodium bisulfate.

Chlorine Stabilizer

• Outdoor fiberglass swimming pools, if disinfected using chlorine, will require a chlorine stabilizer to protect that chlorine from the sun's rays. The preferred chlorine stabilizer for use in outdoor swimming pools is cyanuric acid (CYA). Keep CYA levels in an outdoor swimming pool at 30 to 50 ppm. The initial dose level of CYA for an outdoor swimming pool is 40 ppm. Indoor swimming pools don't require the use of CYA, so it won't need to be added to their water.

Considerations

• Use sodium carbonate (soda ash) to raise pH in a swimming pool and lower it by adding muriatic acid. Maintain your fiberglass pool's calcium hardness at 300 to 350 ppm. Calcium hardness in a pool is a measure of how soft or hard its water is. Raise a swimming pool's calcium hardness by adding calcium chloride and lower it by partially draining then refilling the pool. Always add all swimming pool chemicals strictly according to package instructions only.