1. Reducing agent: It is added in total water intake main pipe of the activated carbon filter to eliminate the residual chlorine in water and prevent the damage of membrane element. 

2. Anti-sludging agent It is added in the water intake of reverse osmosis to prevent membrane scaling and blocking. 

3. Bactericide It is added in the water intake of multi-medium filter to prevent the breeding of bacteria and algae in the subsequent equipment. 

4. Flocculant: The flocculant is mainly to remove the colloidal and suspended particles formed by the insoluble substances, it has functions of removing the turbid and the algae.