I practice the technique that "more is better". I blow out the lines as you describe, then I add antifreeze in about twice the quantity that is advised. Why not? It only costs a couple of bucks a gallon and I just figure two or three extra gallons is a cheap insurance.
I find the three drain valves on our PC to work better and more completely drain everything than the drains on any other RV we have ever owned. They are well positioned and designed.
I have a small "plumber's helper" made for sinks. I use it to evacuate water in the P traps on all the drains, then add antifreeze into them by pouring about a cup or more into the drain. I put a goodly amount in the fresh water tank and pump it for a few seconds to make sure the pump is protected. Also, I open the dump auxiliary drain (leaving the black and gray drains closed since they have some antifreeze in them) and let any excess water in that system drain out. I leave that drain slightly cracked open all winter.
I "milk" any excess fluids out of the Sanipump system hose and I leave the black and gray tank flush valves on the Sanipump system in the open position.
The easiest thing for me to forget is the outside shower hose and head. I never have used those outside shower connections more than twice in thirty plus years of RVing. So, it is easy for me to forget.
When I finish all this procedure, I go into the shop and drink a cup of coffee and do something else for an hour or two, return to the scene of the crime and go over everything mentally as I look at it to make sure I have done it. I once developed my own check list and I suggest it is a good idea. You can keep it by the hot water heater cutoff valve for convenience. Actually, I don't use the checklist until after I do the work, I guess just to see how much more forgetful I am this year as compared to last year
That reminds me: I also remove the drain plug on the water heater and leave it out all winter. Most say that is not necessary, but again .....insurance.
Paul (aka the Winterizer Overkiller)
