If you've got a three way valve to a winterizing hose between the tank and the pump, when you switch it over it'll act as a vent while half open. It'll drop back into the tank if there's anything in it.
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition
I have read here where a lot of you talk about pumping "the pink stuff" through your lines, but not to put it in the FW tank. I guess I am being dense here, but how do you pump it through your lines without using the pump from the FW tank?
My FW has a hose to put in the pink jug and is attached to the pump.
There should be a bypass valve right by your pump with a short length of hose on it, once you turn that valve you bypass your FW tank. Your pump is still used to pump the antifreeze and with the bypass activated it will draw from the antifreeze jug instead of your FW tank.
2011 GMC Sierra 2500HD
2014 Rockwood 8289WS, Diamond Pkg.
I winterize my 2011 Georgetown with compressed air using a home made air chuck adapter. It's a plastic hose cap with the air chuck screwed into a hole I drilled in the cap. My tankless air compressor has a regulator built into the hose and I set it to 30 psi.
The only area that this technique doesn't clear the water from is the manifold area that feeds the water pump. After removing the water filter, I use the winterizing hose to fill that section of pipe with antifreeze. It's easy to tell when this area is flushed because the pink stuff goes into the (clear plastic) water filter canister. The rest of a gallon goes into the traps and the toilet.