To lower alkalinity in a pool, first test the existing alkalinity, then set a target level, and carefully lower the pH levels in the pool by dropping in small doses of acid. Aerate the pool, and test for the alkalinity levels. Cease aerating when the pH reaches target levels.
- Test alkalinity
Test the pool's total alkalinity or its carbonate alkalinity, using drops-based alkalinity test kits. The test kits are available at most department or hardware stores. Avoid using a dealer to test alkalinity levels for reasons of price and efficiency.
- Set a target
If the current alkalinity levels are high, choose a target alkalinity level, ideally 120 parts per million. If high alkalinity poses a continual problem, reset the target to around 100 parts per million.
- Lower pH levels
Drop muriatic acid, dry acid or dilute sulfuric acid into your pool to lower pH levels. Muriatic acid is recommended, but the fumes may be hard to handle. Use small doses of acid to lower pH levels to slightly above the lowest value on the test kit. Do not use large doses, and do not go to the lowest value of the test kit, because excessively low pH levels can damage your pool.
- Aerate your pool
Use a method of your choice to aerate the pool. Methods include using a spa jet in the pool or connecting a fountain to the jet to fill the pool slowly, forcing bubbles into the water.
- Test pH levels, and maintain
Test the pH levels, and continue to add acid gradially until the pool reaches the target alkalinity levels.
If the pool is shallow or small, wait for water return, and apply either of the chemicals to the pool in small portions several times. Wait at least six hours after treating the pool before testing the alkalinity level. Treat the pool again if total alkalinity levels are still high.