I use air and pink RV antifreeze. My dealer winterizes with air only but he noted that when he hooks up his compressed air, he completely dries out the entire piping system. He noted that most folks cannot get their systems as dry as he can and recommends using RV antifreeze after you blow out the system.
I use two gallons of antifreeze. I blow out all the lines first including the spray hose on the sink and the toilet. I hook up the compressor to the city water hookup and make sure the water is expelled from each outlet, sprayer, and low water drains. I also blow the lines with the water pressure bypass system turned in to the normal position and continue to blow with the bypass system turned in the bypass setting. I also drain the water heater from the outside drain.
After that is done, I disconnect the piping that connects to the fresh water pump. That involves unscrewing connection to the pump. I have a hose then which connects to that pump inlet and then is inserted into a gallon bottle of RV-Antifreeze. I turn on the pump and open and close each water outlet until it runs pink. Typically it only takes a little over a gallon to winterize each outlet and spray hose. What is left over I pour into each sink drain to displace any water in the drains and also pour some into the closed toilet so it sits in the bowl. Because the hot water tank is drained and the bypass valves are active, no antifreeze is pumped into the hot water tank. Any residual water left in the tank after the bottom drain valve is removed will damage the tank. I leave the drain plug out rather than putting it back in.
Using anti-freeze will make sure that no water droplets fall into low spots where they could freeze and cause damage. It's really easy to flush the piping when you dewinterize your water system in the spring. I typically sanitize the water tank each spring to kill anything growing in the tank. Pumping that mixture through the water system will also remove any traces of antifreeze and sanitize the plumbing also.
AIR #56 S/OS#15
'04 Classic 30' S.O.,'03 GMC Savana 2500,'14 Honda CTX 700