What does DI cartridge mean in practice?
Mixed cation and anionic resin removes trace ions from RO permeate to very low conductivity levels.
When does it matter?
The color change of the resin is only an auxiliary indicator and the exhausted cartridge may release previously bound ions.
Which solutions are related to it?
Conductivity after DI is checked with an appropriate meter and the cartridge is replaced before the limit required by the application is reached.