Sub-freezing weather and Exposed Tanks.

You will probably get varying answers, but I think you will be fine as long as your motorhome is kept heated, and the daytime highs are above freezing. I've camped many nights in the 20s with no antifreeze and had no issues as long as the unit was kept warm. Also, the fuller the tanks are the more they will resist freezing.

Will you be at a campground with a dump station or hookups? If so, you could just dump your holding tanks before going to bed each night that is shaping up to be cold.

I also suspect you'd be fine without doing anything, but I also won't be around to worry about the mess if that proves to be incorrect. RV antifreeze wouldn't do all that much in the holding tank unless you put a whole lot down. I would suggest rock salt as a better antifreezing agent to use in this case. Even if things froze, though, I don't think it's too likely you'd suffer holding tank damage with your setup. If you have plumbing runs exposed underneath for the fresh water system, they would be a much greater concern for me.

At a minimum I would dump some antifreeze into the tanks and disconnect from shore water at night - inexpensive and no downside.

Windshield washer fluid will do the job and it’s cheaper than the pink stuff. Obviously not to be used in the fresh water tank.

We deal with below freezing temps from time to time in Alberta :)

If the valves are close coupled to the tanks they will not freeze. If you keep substantial volume of fluid in the tanks they will not freeze if daytime temps go above freezing. You are also adding warm grey water from washing and cooking. They take a long time to freeze unless daytime highs are not going above freezing.

Keep a milk jug 3/4 full of water on the picnic table if you are dry camping. The state of the water in it will tell you what is happening in your holding tanks.

I agree with starting with some anti-freeze into the empty tank to protect the pipe and valve somewhat. Once diluted it will not have much effect but then you have the thermal mass of the added water. I expect you will be fine.

If you have electric power you can add some corded tank heaters fairly quick.
www.ultraheat.com

I have never had a problem at those mid 20's temps with exposed tanks on my TC's as well as my TT's.
Use a hair dryer to thaw the dump valve in case it sticks, most of the time that valve will be the first thing to let you know that it's cold out here whizbang.
As said the warm water in those tanks will take a long enough time to freeze when the daytime temps are above freezing. Don't forget to remove your outside water hose at night, use your holding tank and pump for water.

"in the low 20's"

Probably be fine? lol And if it isn't "fine" it will cost you thousands. Use lots of antifreeze.

Good advice guys. Thanks.

We changed our plans a bit... I will fish different rivers.

The weather above I90 is forecast-ed at 28 - 29 degrees F instead of 21 degrees F. 29F is no big deal with daytime highs in the low 40's.

When I empty the tanks, I will start them off with 2 gallons of antifreeze. By the time the antifreeze is diluted enough to stop working, the volume of fluid in the tanks should be enough to prevent freezing.

Next summer, I will install 12 volt heat strips so this is less of an issue.

Thanks!!!


I'm not worried about the valves since the hose couplings are so short.

One thing to bear in mind is the line that feeds water from from the freshwater tank to the pump. Ours is above all the tanks, and no way to reach it. We have tank heaters and a heat tape wrapped around the (long) drain tube from the freshwater tank, and our pump & accumulator are in the same compartment with the water heater (something I wish was true of all RVs!), so even with exposed tanks we have been able to camp down to & just below freezing (overnight) temperatures - of course, temperatures rose at least to the upper 40s in the daytime. However, one night in mid-October in West Yellowstone, our water line to the pump froze up - turned out the overnight low was 16! So we now know our water system's tolerance. (Fortunately nothing broke, and the line thawed out over the next day.)