Deionized water equipment is an ion exchange system. Ion exchange means that when water passes through the ion exchange column, the cation in water and the anion in water (HCO- plasma) exchange with the H+ of the positive resin and the OH- of the negative resin in the exchange column, so as to achieve the purpose of desalting. Different combinations of Yang and Yin mixed columns can make the water quality reach higher requirements. Ion exchangers are divided into cation exchangers (softeners), anion exchangers, mixed ion exchangers, etc. The disadvantage is that the resin needs to be regenerated with acid and alkali after saturation.