Faith,
The anti-freeze you will be looking for is propylene glycol based,
normally labeled as "RV Anti-Freeze" or even possibly "potable". The
colour will be a distinct pink. Normal automotive anti-freeze is
ethylene glycol based and may be greenish yellow or blue. This stuff is
poison and not for your fresh water system. This is the stuff that your
pets will lap up greedily and then keel over from.
If you hooked up to check for leaks you will have water laying in the
low spots of the plumbing, and winterizing is a must. First step is to
locate the drains and open them all. Leave the tank drains open and
close the tank to pump valve. Don't forget the drain on the water heater.
I personally prefer blowing air through the lines, as the anti-freeze
leaves a taste that lasts all summer to me. FWIW. Also I have a 10
gallon water heater that is shoe horned into a spot where adding a
by-pass is not an option. That's a lot of empty space to fill with
expensive stuff just for funny tasting water next spring.
If you go the anti-freeze route it is necessary to take the suction side
of the pump off the holding tank line and insert a hose from the pump
into the bottle of anti-freeze. Turn on the pump and work your way to
the furthest tap and let it run until pink comes out. Then do the same
thing with each tap working your way back toward the pump. This
includes the toilet, and the toilet spray washer. Again, if there is no
bypass on your water heater (there wasn't when the trailer was built) it
will take 6 or 10 gallons just to fill that (depending on the size of
the heater). Not cheap. Figure on salvaging it in the spring from the
piping drain.
If you have an air compressor available and need direction for the
"blowdown" method, let us know.
Matt