RO/DI hooked up to cold AND hot supply

[Myka]

Who has their RO/DI plumbed in so that it's getting a bit of hot water mixing in with the cold? How are you doing it?

Most people just plumb the RO/DI into the cold water line, but I don't want sweaty lines dripping on my finished floors. I don't want to insulate the RO lines to prevent the sweating because I also want to take advantage of the higher product ratio from using slightly warmer water.

I have always just had the RO hooked up to a sink tap and just turned the hot water tap on a bit. Now I moved the system into the laundry room (no sink) and have to figure out how to plumb it into the washing machine hookups. The cold water line is already split for the steam washer and steam dryer, and the hot line is just going into the washer. Can I just split the hot water line and (and the cold water line again) just use butterfly valves to control the hot/cold flow to the RO?

I have a little voice in the back of my mind from my construction days telling me that hot water lines need to have open ends and can't be pressurized. The voice says the pressure from the cold water might back flow into the hot water line and pressurize the hot water tank, but isn't the hot water tank already pressurized? I think there might even be a check valve on the product side of the hot water tank maybe?? Maybe I'm overthinking it and the little voice needs to shut up...