How much waste water does a RO unit produce?

[MitchM]

Temperature makes a big difference too.
I had an inline thermometer on my household water supply just before the RO unit.
In the winter, sometimes the incoming water temp was below 5 C!
The RO membrane rejection rates (and GPD) are also based on an incoming temp of 23 C.
The colder the temp, the higher the rejection rate.
I have heard of some setups supplying the RO unit with a mixture of hot and cold water.

Mitch