I have to install a utility sink in my unheated garage (I don't think I have ever seen it below freezing) for my wife's new business... the floor of the garage is a foot lower than the first floor of the house (built on slab).
My unfinished utility room is on the opposite side of the wall. The utility room has the stack on the far side, and incoming cold water and hot water tank.
I plan on running PEX from the hot and cold lines (copper) to two frost free taps over the tub (probably not necessary but may as well so they can be weatherized if needed).
For the drain i believe my best option is to use a under sink sump pump with a 8 foot header then less than a two foot run to an existing 2" drain pipe with a vent behind it that runs right into the stack a few feet further.
The pump I bought also needs venting and that is right there as well (or I can use a cheater?).
I am leaning towards taking the drain and vent into the wall to the warm side right after the check valve so that any leaks at the check valve would be into the garage. With the water that will always be in the pipe there should not be any chance of freezing in the check valve.
The only place it might freeze would be in the pump tank, but I could always wrap it with heat tape if needed?
Your thoughts would be appreciated.