The main difference between ASTM Type 2 (pure) and ASTM Type 1 (ultrapure) water is conductivity. For ultrapure water, the conductivity is a maximum of 0,055 µS/cm. For pure water, it is maximum 1 µS/cm. Other quality parameters that differ are sodium and chloride concentrations, which have a maximum level of 1 µg/L and 5 µg/L, respectively. To produce ultrapure water, you need a DI cartridge, designed for producing ultrapure water, for polishing. In comparison, to produce pure water you can use either a DI cartridge or an EDI module suitable for producing pure water. Depending on water purification system and feed water, a pretreatment step may be needed.