how cold

FWIW: I am very strongly of the "blow it out with air" persuasion when it comes to winterization. In almost a decade of Pennsylvania winters, this has worked very well for me, and is certainly easier, cheaper and more pleasant than getting that...stuff...in my water system.

I had a freeze up when I turned on the water when I got to Mission, TX. I failed to run anti freeze through the hot water on kitchen sink. Burt Ogden RV fixed by soldering broken pipe when couldn't find replacement faucet for $90.00.

If your rig is plumbed using PEX, the danger is significantly reduced. Although the manufacturer won't quite come out and say that PEX is freeze-proof, the fact is that it is quite robust to freezing. It is really the fixtures, traps, and dump valves that are at most risk. If the fixtures are all in heated areas and you keep antifreeze in the waste system, you have significant head-room. Often, the long pole in the tent is the outdoor shower. I am currently working on making our rig 4-season, and that fixture is one of the biggest issues. I am thinking of adding valves so that it can be separately winterized.

well...even if the water in your tank is storing daytime heat...little of that will transfer to the lines.

you can turn your taps to dribble water and that'll move warmer water from the tank to the lines.

it's a judgement call which can be pricey

mike

The answer to this when I asked an RV tech was two days at 28dF to 32 at night is OK as long as the days go well above freezing. More than two days like this and you better winterize.

So you are right on the edge. Problem is the forecast says 27 or 28 and it gets to be 22 that night and you have costly repairs from frozen pipes and valves.

When water freezes, it expands. Water freezes at 32 degrees. How fast the water will freeze is a function of the amount of water (mass), the ambient temperature (the colder it is, the faster the water will freeze), the time water is exposed to freezing temperature (the longer that time the more likely water will freeze) and the wind chill (how fast the mass will reach the ambient temperature). Anytime a pipe with water in it is exposed to freezing temperatures, there is a risk of damage. What your risk tolerance is only you can answer.

It's not the cold that gets you it's how long it stays cold. If it just drops down to 27 for a couple of hours during the night no problem at all but if it get to 27 and just stays there for days OH yeah things are going to start to freeze.

it all depends on how long it stays at or below 32. if it just quickly drops down and bounces back up, no problem. if it stays under 32 for many hours, might be a problem.
bumpy

You'd be ok.