I originally purchased a RO (Reverse Osmosis) filtration system from Costco. It only last 3 months before the water became trickling. So I bought this UC300 on Costco again to replace the RO system. It's much easier to install and the water quality is great. The RO system has 4 filters but the 4th filter is mostly for filter the water from the tank. So I really prefer the water does not store in the tank first.