Bruce,
Since you're in MI, you know that you will either need to heat the shop to keep the water supply and drain lines from freezing, correct?
Or, you can do as a friend of mine did, he has his water supply buried 5ft and then rising up inside the bathroom area, mounted all the piping on 2" blocks on the inside of the bathroom walls (prevents pipe sweat from damaging his drywall & it allows air circulation around the pipes). He doesn't heat his entire garage - only the bathroom, so all's well there. He also installed a water hose faucet in the bathroom. He didn't install a hot water heater - rather only has cold water at his hand basin.
Or, you can plan on running your pipes to allow you to drain the water out of them and not use it during the freezing months.
Or, you can blow ALL the water out of them (via an air compressor), and again, not use it during the freezing months.
Unless you plan to run your pipes like my friend did (on the inside of the wall board) try not to layout your bathroom piping inside an outside wall, as the pipes will be much more apt to freeze (even if their insulated and well heated) than if you would have it on an inside wall.
Personally, I don't heat my garage but I do have a "seasonal use" old double basin laundry tub to clean fish, wash boots, etc. - stuff I don't want to wash in the house. I also have a 20-gallon electric hot water heater (even tho I have natural gas at the house, I didn't want to deal with a vent stack & hole in my garage roof). The electric water heater is mounted on a shelf above the sink, making it easier to drain in the Fall. Since I don't have a need for hot water real often, I don't leave the power on it 24/7, rather turn it on and 30 minutes later I have hot water; when I'm done, I turn the heater back off. I installed a switch on the power supply to allow easy on & off operation, as needed. My water supply comes from my house and is controlled via an underground valve (similar to what most city supply lines have at the property line). The valve is accessed via a piece of PVC pipe to the surface, which allows it to be turned on & off with a 5' long fork wrench twice a year. A bird bath sits on top of the PVC stand pipe, making it easy to locate twice a year and I don't have to wrestle with a cap or cover. My supply water line from the valve to and into the garage drain back to the underground valve. When the valve is closed, it opens an exhaust port which allows the upland water to drain back & out and into the gravel that was placed around the underground valve. The wash tub is located on an outside wall and drains (without a trap - no chance of freezing now) thru the wall, down out into a 10' section of peforated drain pipe buried in gravel just below the grass. Because it isn't septic water, it doesn't stink.......
Why don't I have a toilet in my garage?
1) Because I didn't want to give up the necessary garage space (I don't have enough now!) that a bathroom would of taken up (my tub sink doesn't need walls),
2) I didn't want to mess with any sort of septic system that had to deal with solids,
3) A urnal could of been installed, but then I'd need to remember to dump RV antifreeze in the trap & I'd be back to at least half walls, and
4) I sure don't need any more additional weekly cleaning chores!
Good Luck!
RW
