I suppose the term "Winterization" takes on a whole different meaning for folks from different parts of the country. And, there seems to be an awful lot of broad brush painting of how/what is the best method.
For those living in 'warmer' climates, either just draining at the low point drains or a simple 'blow-out' most likely
is all that is necessary for them. If it works for you, well all is well and good then.
For those like me, living where it gets really cold for extended periods of time, (I'm talking months where temps never get above freezing and usually is below 0º) the winterization process really takes on a whole new meaning.
I start out by draining everything as best as possible through the low point drains. I always try to do this when LEAVING our campsite on the last outing of the season if at all possible. I simply open the low points, (leave them open) then crack open ALL the inside faucets and drive home.
By the time we get home, the rocking and sloshing of travel really does a super job of removing the water from the system.
Don't believe me? Try this sometime... after draining EVERYTHING you can from the low point drains, (no air) close them back up and take your rig around the block two or three times. Pull back in your driveway and re-open the low point drains. I GUARANTEE additional water will come out.
Then, I blow out the lines (including the black tank flush) with compressed air.
I do this for two reasons...
1. Even after the drive home, I always get some residual water by blowing with compressed air.
2. I can be 99.9999% sure once I start adding antifreeze that when I crack open a faucet, it will be 99.999% pure antifreeze. I use less antifreeze because I don't have to let it run an extended period of time hoping I've got the water flushed out ahead of the antifreeze.
In our climate, it is imperative to add antifreeze.
One drop of water in a pump head or faucet valve can cause havoc.
I have seen it on more than one occasion.
I did not touch on bypassing the WH, cracking the city water check valve, checking the water filter canister, adding antifreeze to the traps and tanks, etc., etc. as they have all been beaten to death. If you own an RV and do your own winterizing, you really should know about those anyway. If not, maybe the procedure is better left for the dealer/service center.
One more thing... my water system never sees 'contaminated' compressed air. I have a water/oil separator and a desiccant filter on my shop air compressor. I also realize some folks might not have these things with a typical 'home' air compressor but then again, most typical 'home' air compressors are oil-less (meaning they pump via a diaphragm and not an oil bathed piston) so contamination from within is nil and unless they are using their compressor in the middle of a dust storm, contamination from outside is nil as well.
Here's hoping you all winter well.
Looking forward to the warmer months when we can discuss whether it is safe to use bleach to flush the system for summer!