What the dealer guy told me is to open all the faucets, hot and cold, depressurize the system, then drain the water heater, then open the low point drains. That will pull water away from the faucets, the pex can handle things after that. Personally, I like throwing a little antifreeze in there just to be sure. It's cheap, usually pretty easy.
Now-2014 Sierra 346RETS 5er BUB
Then-2002 Keystone Springdale 286RLDS TT
Nights camped in 2014-28, 2015-127, 2016-10