Changing the CR Spotless Replacement Resins is simple and can be accomplished in less than 5 minutes. Simply unscrew the clue watertight housings and remove the resin cartridges. Properly dispose the used resin (it is a non hazardous material but will be slippery if spilled on the floor so be careful!), rinse the cartridge, and refill with new resin. Place the cartridges back inside the housing ensuring the whit cap is in the bottom of the blue housing (black washer still attached to the top), replace the centering ring atop the cartridge and reattach the body of the unit.