The simplest configuration for ion exchange demineralized water treatment is a two-stage bed system composed of a cation exchanger and an anion exchanger.

Some single-stage two-bed demineralization systems adopt the unit system, in which each unit consists of one cation exchanger, one (decarbonator), and one anion exchanger. During operation, both the cation and anion exchangers are regenerated simultaneously, regardless of which one becomes exhausted first.

Other single-stage two-bed demineralization systems adopt the header-pipe system (common manifold system), where cation exchangers operate in parallel with each other and anion exchangers in parallel with each other. Only the exhausted unit is regenerated individually.