"I haven’t had much of a problem with water spots on my cars, but you guys know me. I’m always in favor of overkill. Seriously though, this thing is pretty sweet. I use it with my pressure washer to preserve the resin as much as possible.
The idea here is to “deionize” the water to ensure you don’t have any contaminants or minerals that can dry and leave spots or etch the paint. I still blow dry the car, but this makes me not have to worry about any hard water spots.
You will want to buy another two sets of MTM Quick Disconnects to make connection easier."
These resin replacement cartridges are easy to install and virtually hassle free. You can change the resin cartridges in less than 5 minutes. Simply unscrew the watertight housings and remove the spent cartridge. Then, put the replacement cartridges inside the tube and reattach it to the body of the unit. You'll receive two 20-inch replacement cartridges that will deionize approximately 100 gallons of water each.