Using over the winter - do I need to winterize

the only way I know to not winterize properly is to blow out the system. then you stand the chance of water settling back into low spots. can do the winterizing the right way with antifreeze and drain and blow that out collecting the antifreeze for reuse. if you reclaim antifreeze I would blow out the system first so there is only a little dilution.
and no, the proper chemicals are safe
bumpy

You have two options for the motorhome when it's in freezing weather (assuming it's a cold weather capable unit, i.e. the plumbing is enclosed within the heated part of the motorhome). Either you keep the motorhome heated above freezing, using say the furnace or by storing it in a heated indoor storage facility, or you winterize the plumbing system.

Winterizing isn't hard and the materials required aren't that expensive. If you have an air compressor and so can blow out the lines with air, the materials are downright cheap--just sufficient RV antifreeze to put a cup in each of the drain traps. If you instead displace the water with antifreeze in the pipes, it could be a couple gallons or so, still not very expensive.

I use the compressed air method with my motorhome. I start by draining the fresh water tank, the plumbing as much as practical with the low point drains, and the water heater; this means opening a few valves and the various taps on the sinks etc., removing the water heater drain plug, and then going away for several minutes while water dribbles out onto the ground. Next, I bypass the water heater, run the pump for a bit (to get water out of the suction lines and pump body as much as possible--it's OK to run RV water pumps dry for a minute or two), and hook up the compressor to the city water inlet via an adapter I pieced together. The compressor's regulator is set somewhere around 40 psi. Next, I successively open individually each of the taps and the low point drains and let the air flow until no water drops are spitting out, usually going around a couple of times. Then it's just disconnecting the compressor, shutting valves, and pouring a cup of RV antifreeze down each drain and into the toilet bowl, and draining out the bit of water I just put in the holding tanks.

All told, it's maybe a half hour of work and a dollar or two of RV antifreeze. Dewinterizing is equally as easy: put the plug back in the water heater, unbypass it, and sanitize and fill the water system. I do usually try to check for leaks beforehand with air pressure. The check valve in my city water connection vibrates when air flows through it, which makes checking for big leaks fairly straightforward: just listen for that sound.

“Do I need to fully winterize and unwinterize the motorhome each time?”

The downside of not winterizing is the expense of fixing the RV if water freezes.

and don't forget to put some antifreeze in the drain traps, etc.
bumpy

I prefer the pink stuff method. Once you do it a couple times it should take you about 30 minutes. All you do is drain all the tanks completely, Set you water pump to winterize and draw fluid from the gallon jugs through the lines. Make sure to get some in each drain trap. Your water heater should have a winter setting on the valves. You should get by with 2 or three jugs which you can buy for about 3 bucks a piece. Remember you are not filling any tanks with pink stuff just the lines and traps. Really easy and a lot easier than a broken pipe. The pink stuff is non toxic. Blowing out the lines works also I have done both but feel more secure with running the pink stuff through the lines. All though I haven't broke a pipe yet in twenty years with either technique. JMHO

Do not forget to bypass and drain the Hot Water Tank. DO NOT put any pink stuff in the Hot Water Tank or the Fresh Water Tank.

Yes, you must do it between trips.

Also, keep in mind when you return from warmer climates in all likelihood you will need to dump your holding tanks before you head North. Why, because the CO dump stations may be closed during the off season.

lfrese wrote:

Do I need to fully winterize and unwinterize the motorhome each time? Is there a way to avoid this? It seems like it would be an expensive thing to have to do and undo multiple times during the winter.

Not being a smart a$$, but you only have to winterize your RV anytime you don't want the water pipes to freeze and burst. You live where it gets very cold for days on end. Not winterizing will guarantee you a repair bill in the spring.

Between uses if, and that is a big if, the weather does not go below freezing then you are safe. Otherwise, you must winterize or keep the RV heated to prevent freezing.

The chemicals flush out well, and I know of no one having any ill effects from using a system that was winterized.

You can try blowing air through the system but that is not fool proof.

Since the weather forecast for Denver is a low of 26 degrees on Monday and Tuesday night, and 27 on Wednesday, it would be a good idea to winterize your rv this weekend. I plan to do mine in the next day or two.

We use our DP in the Winter as well. Here in Michigan I thoroughly blow out all the water lines, open the low point drains, drain all the tanks including the WH (which is set to bypass), disconnect the ice maker and blow out, and add antifreeze only to sink/shower the traps and toilet. This is done after each trip.

DownTheAvenue wrote:

You can try blowing air through the system but that is not fool proof.

How exactly is using compressed air to winterize not foolproof, or at least any less foolproof than pumping antifreeze through the pipes? Air doesn't freeze and expand, any more than RV antifreeze freezes and expands. Any slight hint of moisture left in the low points in the plumbing has plenty of space to expand and doesn't burst the fittings. Both are perfectly sound approaches towards winterizing an RV, and there are many, many RVers who use each with success every year.

Seasonal homes and camps with plumbing systems are typically winterized by blowing the water out of the pipes with air (if they aren't designed and built in such a way that the system can be drained by gravity). Many of them have metal pipes that are far more likely to burst if water freezes in them than are the PEX pipes used in RVs.