[JRTJH]

The faucet cartridge (hot and cold) in an RV faucet holds about a tablespoon of water. The toilet valve in an RV holds about the same amount. There are 4 faucets in my RV (kitchen, shower, vanity and outside shower) plus the toilet flush valve. Any one of those faucets costs 5 times the price of 2 gallons of RV antifreeze ($25 for a cheap faucet/$5 for 2 gallons of antifreeze).

RV antifreeze does not expand when it freezes, so any antifreeze trapped in a faucet cartridge or in the toilet flush valve or even in each of the P traps, won't expand and damage/destroy the faucet. Almost all of the "Phoenix, Flomax or Lasalle Bristol faucets that I've seen do not have repair cartridges available, so if one is damaged, you will need to replace the entire faucet.

If an RV plumbing system were "perfectly level and always drained to the low point drain caps" and if every tablespoon of water were blown out of the plumbing system using "air only" then I'd agree with you....

That said, living in a place where it regularly drops below 0F and often below -20F for weeks on end, the price of antifreeze is a "no brainer" compared to the risk of having to replace even one faucet or a P trap under any sink.

To me, the "added insurance" makes for less apprehension in the spring when I pull the trailer out of the pole barn and hook up the city water to the trailer....

For me, is it "mandatory"? No, but is it "reasonable" ? Certainly....

I don't like paying the thousand plus bucks every year for liability insurance on our vehicles and on the house, but that's "cheap" compared to having one problem in an accident or ???? For me, it's the same with the $5 in RV antifreeze. Just displacing the water remaining after using the compressed air is enough "added insurance" that I can "rest all winter without worrying about the trailer while it's in storage".... YMMV