Typically CO2 dosing is used for pH correction in many pool plants, the addition of acid dosing allows for fast pH correction and greater control of total alkalinity. Further, the flexibility of having two different chemicals for pH correction gives greater reliability and continuity to dosing regimes when CO2 falls into short supply or deliveries are unreliable.
Acid dosing can be either a liquid (Hydrochloric Acid) or dry (Sodium Bisulphate – mixed from dry by a chemical mixer and stored within a vessel).
The recent trend is towards the dry acid systems due to the materials handling and storage issues.
There can be significant cost savings.