SERparacord
Grandmaster
This unit is sold at Lowe's (and maybe other locations) Last I checked, while they sell the unit, they don't sell replacement cartridges.
R.O. filters useful life is based on consumption. Don't use it, they can last for years, use it often and they may last four months.
R.O. water regeneration slows down when filters require replacement.
If thinking of buying one, there are models for City water and models for well water. They are different.
R.O. water for the concerned homeowner is the the way to go.
That's where I got my replacement cartridges.
http://www.lowes.com/Search=what+fi...0&newSearch=true&Ntt=what+filtration+systems#!