Zero Waste RO

[sphelps]

There is always room for improvement, I hardly see how a system that wastes more water than it produces is flawless.

How about a simple pressure switch and solenoid valve to control when the RO system is allowed to produce water?

A pressure switch on the hot water water line will activate a solenoid valve when hot water is being used.
The solenoid valve feeds the RO unit.
Waste water from the RO is fed into the hot water line before the water heater.

With this method waste water is only introduced when hot water is actually being used, such as laundry, dishwasher, shower, ect. This will not decrease the efficiency of the hot water heater and will not allow waste water to enter the cold supply. In addition an accumulator could be used on the waste water line which will allow some waste water to be stored before hot water is used and discharged more quickly when hot water is used.