Test the water in your hot tub for the level of sanitizer. Use a spa test kit and follow the directions for testing the chlorine or bromine level. The normal level of sanitizer is 2 to 3 parts per million. Add a small amount of bleach from a plastic cup and test again in an hour. Wear rubber gloves while handling the bleach. Add more bleach if the level is still too low. If the level is too high, drain one-quarter of the water from the tub and replace it with clean water.
Determine the pH level of the water by using a test kit and following the directions for testing the pH. The optimum pH level is 7.0 to 7.8. If the level is too high the water is too alkaline, and if it is too low it is too acidic.
Add a capful of drain cleaner to the hot tub if the pH is too high. Drain cleaner has a high level of acid in it, which lowers the pH. Wear rubber gloves when using the drain cleaner to protect your skin. Allow the drain cleaner to circulate for an hour and test the water again. Add another capful of drain cleaner if the pH is still too high.
Sprinkle a cup of baking soda in the tub if the pH tested too low. Baking soda is a base material that brings down the acidity of the water and raises the pH. Test the water in an hour and add more baking soda if the pH is still low.