Winterizing a Trailer Procedure

JaxDad wrote:

garyemunson wrote:
The best tool to own is a battery powered compressor with a regulator you can set at 40 lbs.

In theory, a 1/4" air fitting running wide open, like when blowing out a water system, with the feed pressure at 40 psi will flow a little over 25 CFM.

A decent small 120 volt compressor with a 2 gallon tank might be able to make 5 or 6 CFM at 40 psi.

The only way you'd get enough volume of air with a battery powered compressor would be to fit an air tank inline with the hose and create a reservoir of pressure to give you full pressure for a much longer period of time, however you'd likely burn up the compressor in no time doing that.

Not sure where you get that 1/4" as a requirement, or even typical. If you look at made-for-purpose RV blow-out plugs, the brass ones have an orifice much smaller than 1/4", and others have Schrader valves which also very much restrict flow.

It would be a very large RV to have more than a couple of gallons of capacity in the water lines. I know a single gallon will fill the lines on our (relatively modest) one with more than enough left to fill the traps. It's more volume than pressure that's needed to blow out lines - you really only need a few psi to push the water through. A 2 gallon air tank at 40 psi will deliver over 3 gallons of 10 psi air.

And really, you don't even need that - just constant flow. Open the valves one at a time starting closest to the source. After you get rid of all the constant water flow (so they just sputter), let the system pressurize, then go back and open one at a time, the air pressure in the lines will blast out most of what remains. Run the pump briefly with the supply valve closed and the antifreez line open to clear it. Then open all the valves and the low point drains and let the few remaining drips come out. Any left after that shouldn't be a worry, there will just be little bits here and there surrounded by enough air that there's room for freeze expansion.