[mike31154]

There's a trade off to the better production ratio eh? IMO, save yourself the hassle. Not only are you using more energy for a bit or warm water, but the rejection rate with warmer water is worse, so you'll burn thru DI media faster. Personal experience with my unit in winter vs summer - summer RO TDS @ about 14-16 degrees C incoming water temp = 1. Winter RO TDS with incoming water @ about 8 degrees C = 0. I can live with a slightly lower production rate thank you very much. Incoming TDS for the most part is in the 160 to 170 range in my humble abode. That's Kalamalka Lake water. On the rare occasion they switch us to Duteau Creek source, TDS drops to 50!