# A Newbie's Guide To Rv Antifreeze



## 4RovingSongsters (Jun 22, 2011)

In winter the weather turns cold. How cold, depends on where you live. To a Floridian, 60 F is cold, but the concern with RVs starts at 32F. Once the mercury drops that low, pipes can freeze if they're not protected, and the repair of split RV pipes is, to say the least, expensive. So, we winterize our units. (Note: there's more to full winterizing than just antifreeze, but I'm concentrating on this narrow topic. See the many other helpful topics on this forum.)

Winterizing principally consists of removing water from the tanks and pipes, and/or replacing it with RV antifreeze. Many have posted the details of this process, and I'll not belabor that topic from my relative inexperience. But I did discover data about the antifreeze itself that I haven't seen here before, so here it is.

*Which Antifreeze?*

Typically, you'll see product on the shelves at CW and WM with the label promising -50 F protection. That doesn't mean it'll protect your RV at that temperature. In reading the fine print on one of these bottles, I learned that -50 means it'll prevent a copper pipe from bursting above that temperature. A PVC pipe like what's in my TT will burst at -10F !! Whether that's good enough depends on where you are: here in northern NJ I've sometimes seen -20 F every morning for a week, so -10 burst protection isn't nearly good enough. I dug deeper.

RV antifreeze is based on propylene glycol(PG). This is a food-grade industrial chemical that like its toxic cousin ethylene glycol(EG) (used in engines) inhibits ice formation in a mixture with water, but unlike EG is safe when present in residual quantity in potable water systems. There are different levels of antifreeze corresponding to different concentrations of this principal ingredient. The freeze protection afforded by each offering is labelled on the bottle, but as mentioned, doesn't offer what you expect. I have found products labelled for -50F, -60F, -100F, and -200F, but all referencing burst copper pipe. Per the label examined above, the protection level for PVC, owing to its lesser tensile strength, is about 40F higher. So for me here, safety requires using at least the -60 product, and up in the plains where some of you are, -100F would be required.

As mentioned, this is about pipe burst temperature. The stuff actually does freeze above these temps: "-50F" solution freezes at +10F and expands enough to burst your PVC at -10F, copper at -50F. And this is when tested in brand new pipe. Yours may have some prior stresses that weaken it further.

*Antifreeze Freezes*

I found some useful data in Wikipedia's "Propylene Glycol" article but the important part of it is:

Freezing Points of Propylene Glycol/Water Mixtures vs. Percent Propylene Glycol
%......°F.....°C
0......32......0
10.....26.....-3
20.....20.....-7
30.....10....-12
36......0....-18
40.....-5....-20
43....-10....-23
48....-20....-29
52....-30....-34
55....-40....-40
58....-50....-46
60....-60....-51

This clearly shows that if I want to avoid freezing in NJ I need to use solution that is at least 50% PG. This roughly corresponds to the -100F products (actually about "-85F" at this concentration) and gives me a measure of burst prevention in PVC down to -45F. More expensive at ~$11.00 per gallon vs. $4 for -50F, but still cheap insurance. (I also found limited offerings of 100% PG, which would allow me to mix my own ideal concentration, but it's pretty expensive.)

Of course it also strongly justifies owners who first blow out the water, then pump in antifreeze, _then _blow that out too. This leaves only a residue of antifreeze, supposedly too little to collect and freeze damagingly in pipes. But the bottom line is to think hard about your own situation and play it safe to avoid springtime heartbreak.

Happy camping!


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