The post de-ionizer takes the small percentage of contaminants that the membrane could not remove and filters this to greater than 99.99% pure water.
It will give you 0 ppm TDS, Conductivity attainable less than 0.1uS/cm or resistivity of close to 18 meg.ohm
Excellent in areas with hard water. Produce 99.99% pure water. It can give you 0 ppm TDS**, Conductivity attainable less than 0.1uS/cm.
When used in conjunction with a Reverse Osmosis system
Approx 6 Months
** Zero TDS subject to in coming water quality flow and temperature