Water needs per person in the household are around 2 gallons per day. To have a fast recovery on your tank, nowadays systems have 35 GPD Membranes and up to five stages of filtration. To produce about 8 gallons of water per day, such system sends far more than 80 gallons of water down the drain. Actually on the top portion of your tank a 35 GPD membrane makes only around 15 GPD. Now with the permeate pump, you could go to a 15 GPD Membrane and still have the same amount of water that you used to get from your unit.
If you used to sell
100 GPD systems for a light commercial system, you could now use a 50 GPD
system with a permeatepump.