When you see the pink liquid coming out all outlets and faucets, and poured in the traps. That pretty much says it is winterized.
With air, how do you know for sure all water is out? Is there a downside to the rv antifreeze other than $ ?
You know that all the water is out when no more water comes out. OK, that is a little snarky, but really, it is obvious when you are done.
The procedure:
0) If you have a hot water tank, drain it. If you have a bypass, use it.
1) connect the pump to the city water inlet through an adaptor.
2) Turn it on and let a bit of pressure build up.
3) Starting with the fixture closest to the pressure source, open the cold water outlet. if you have a low-volume pump, you will lose pressure after a few seconds. Just close the valve for a few seconds and let the pressure build up again. Open the valve. If any water comes out, repeat.
4) Do the same with the hot water outlet.
5) Repeat for each outlet, working your way outward, away from the pressure source
6) Wait 10 minutes and repeat the whole process. There will be very little water this time.
7) If you have any removable shower heads or other fixtures, consider moving them into the house for the winter.
8) If you have a Keurig coffemaker, take it indoors.
9) If you have a water filter on your pump, you may want to unscrew it to empty it. Mine seems to empty on its own, though.
10) Pour some yucky pink stuff into all your drain traps.
11) Pour the rest of the gallon into the grey tank and run the macerator until you get pink at the end of the dump hose.
Done! Takes maybe 30 minutes with practice. I often do it 2 or 3 times a season, between cold-weather trips.
Other than $ the downsides of pink stuff are (1) takes longer; (2) tastes gross; (3) needs to be undone every time you want to use your fresh system; (4) messy. I see no advantage whatsoever to using it, other than it perhaps being slightly more forgiving of sloppy execution. But, if you do a double blowout, it is pretty foolproof.