http://pop3.dcc.edu/vettenet/garage.html
Has a bunch of notes about building a garage. The first item is rather
controversial: whether or not to use PVC for air plumbing. Some folks say
it's fine, some say that it's not designed for the high pressure
differentials when the compressor comes on and off, that it gets weakened
and breaks at the bottom.
There's enough controversy that I'm staying away. The other choices are
black iron (a traditional favorite), galvanized steel, and copper.
Black iron has a potential problem with internal corrosion. Galvanized
costs a miniscule amount more and has no such problems. They both require
that you either buy pre-threaded pieces in the right lengths, or buy,
borrow or rent a cutter and threading tool.
Copper is really not that much more expensive, surprisingly enough. The
fittings have to be sweated on, of course. I still haven't decided what to
use: copper has high coolness factor, but is hard to reconfigure - on the
other hand, I plan to put my pipes behind drywall.
A few other ideas: put a solenoid-operated valve on the output of the
compressor, and make the compressor's power supply switched, with the
switch inside the shop. That way the unit won't cycle in the middle of the
night, and just in case something happens and there's a blowout when you're
not there, the compressor won't run trying to fill the hole.
An alternative to running the line high is to start low and work your way
up: have the main line slope towards the tank and water trap, and all the
outlets above the main line. Then you only need on drain, and it's at the
water trap. Put an automatic drain on it and don't think about it any more.
I have a double-tub laundry sink in my current garage and it's wonderful.
The new garage has cold water; I'll probably put a sink outside in the
back. I may hook up to the sewage line, but I'm also considering digging a
small gravel pit and directing the drain there. I rarely dump chemicals
down the sink - it's mostly for washing up or cooling hot items.
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