Winterizing with Air

[Ray,IN]

You cannot successfully winterize plumbing "P" traps with air, nor can you winterize a clothes washer with air.
If you replace the "P" traps with HepvO drain valves you eliminate the need to winterize them, but you still need to add RV antifreeze to the holding tanks as previously noted.
Next time you "winterize" with only air pressure, continue winterizing with RV anti-freeze, catch what comes out of the faucets until solid pink antifreeze shows. Measure how much water you catch.

[SlowJoe]

As has been mentioned, I also winterize by blowing the lines and then use antifreze. I made an adapter to connect the airline to the garden hose supply connection. I then open all faucets/valves one at the time and allow the water to blow out. If your compressor has limited capacity it is fine to close the faucet to let it catch up. I usually do this anyhow to let the water collect in low spots and then "burp" the slugs out because it seems to help get more out of the system. I do them one by one until no (or maybe just a few drops) of water continues to come out. I then go through them all once more to ensure nothing else comes out. Next, I pour antifreeze into the hose, reconnect it and go open valves one by one until I see the antifreze at the faucet. I refill the hose with antifreeze as necessary. In my view this method has several benefits. Less antifreeze required, less water in the system for the antifreeze to protect against or be diluted by, supply lines which are relatively empty and more likely to be unaffected by freezing. My final step is to pour some antifreeze into each drain with a p trap to make sure they do not freeze. I make sure waste tanks are empty and pour enough into the drains to ensure some makes it into the gray tank. I also add some to the black tank and leave a bit in the toilet bowl. One other step worth mentioning is that the icemaker valve either needs to have antifreeze cycled through it or removed and blown out. I remove mine and store inside a heated space since it seems to be the easiest and most certain way of protecting it. Make sure you get antifreeze in your water pump as well as the HW heater as others have mentioned.

[Bobby F]

Let me just add that, if you're properly running antifreeze through each faucet, you've already filled the traps with it. No need to add more.