A little research proves that salt rejection is better at cooler temperatures, so my comment was way out in left field.

4:1 is a claim all manufacturers make, but that assumes no back pressure - which would be true if you were not filling a tank. Do many folks really just dump it to a bucket? I don't...

My only experience with permeate pumps is with Aquatec. They claim to improve a host of things...I only know that they have worked well for me for some 15 years.