A reverse osmosis system is 25% efficient. A washing machine and dishwasher uses electricity and hot water (which takes energy to heat) and WASTES EVERY GALLON OF WATER THEY USE. A reverse osmosis system is not nearly that wasteful – no electricity and no wasted energy with heated water.
Where does RO waste water go?
In reverse osmosis, there is cross-flow filtration through the membrane. The permeate stream (product water) goes to the storage tank, and the waste stream with all the contaminants and dissolved inorganics goes to drain (also called concentrate stream or RO reject water
How much water does RO filter waste?
An average RO purifier wastes approximately 3 litres of water for every 1 litre of purified water. That means only 25% of water is purified and 75% of water comes out as waste.
PUTTING IT IN PERSPECTIVE
Your reverse osmosis system will use 1% of your annual household water usage annually. The average family RO will move roughly 12 litres to the drain every day. If you compare this with a shower which is the biggest consumer of water in your home with the average shower using 40-60 litres per shower. Or every time you flush your toilet up to 10 litres can be used. As RO water is only used for consumption the amount of waste is minimal.