Reverse Osmosis Undersink Drinking Water Filter System 50 GPD pumped5 Stage Reverse Osmosis Water Filter System 50gpd At present, reverse osmosis is the best method to produce pure water via a physical system (without using chemical products). Removes THMs Trihalomethanes from your drinking water. The water enters the system then goes through the sediment PP 5micron water filter cartridge which is stage 1. Then the water goes through an activated carbon filter and then a carbon block filter. In this phase of