If you don' know by now, it is suppose to so called leak to the drain. Lots of wasted water 5 gallons wasted to 1 gallon drinking, that is crazy, I'm going to have to buy something better. Below was copied:



Reverse osmosis water filterIf your water harbors unusual contaminants like nitrates or perchlorate, a reverse osmosis filter is the only way to get rid of them, experts say. The Whirlpool Gold WHER25 is less expensive than other RO systems, and it performs almost identically to more expensive systems in comparison reviews. Reverse osmosis systems remove almost every contaminant you could possibly have in your water. But they also filter out "good" minerals such as fluoride. The process wastes about five gallons of water for every gallon of purified water produced, and it flushes contaminants back into the water supply. Therefore, reverse osmosis should be considered only if you have specific contamination problems.