The only way to lower your cya level in your swimming pool is to partially drain your pool and fill with fresh water that will lower it or if you want to lower it to almost nothing completely drain your pool and start over but keep in mind chlorine tablets will raise your CYA level
More information in the related link below.
You have to know what you are doing. The addition of muriatic acid lowers the pH and total alkalinity in swimming pools.
Reduces alkalinity of swimming pool water (softens hard water)
Sodium Bisulphate is dry acid for swimming pool use.
That Acid is called Muriatic Acid. You put it in your swimming pool to lower the PH of the water. At lower PH Levels, the chlorine you use to sanitize the pool is more active, as a disinfectant. You MUST be careful not to put too MUCH Muriatic Acid in your pool! PH that is too low will create potentially deadly fumes, so test your water. Low pH is corrosive to plaster and metal pool parst.
It lowers PH
The use of small amounts of muriatic acid added to the water will help reduce or lower the pH and alkalinity. Keep testing and adding acid frequently until your have reached 7.6 - 7.8 range. Ken
Rain if it is acidic can lower the pH of a swimming pool.
Turn the pool upside-down and knock on the bottom.
rain and acid wash
Most likely not.
Muriatic Acid
nothin