How Do I Prevent My RV's Holding Tanks From Freezing During Winter?

by Liz McDade
(BIloxi, MS)

How to Keep Your RV's Holding Tanks from Freezing

How to Keep Your RV's Holding Tanks from Freezing

I am staying in an MS campground, and when the temperature drops to between 25 and 32, we were told to keep the dump valves cracked partially open and let the water run in a small stream all night to avoid freezing. Last night when I did that after first dumping a full tank of black, then gray - I awoke to the sound of water dripping, and it wasn't the sink. Somehow the black tank became full of water from what was running in the sinks and had backed up into the toilet bowl and was overflowing. I had to go outside and pull the valve completely open on the black tank - then all the water went down. Now I have a very wet bathroom carpet - out into the walking area.

Is this what I should have done? Without winterization and living in an RV when the temperatures drop, what IS the correct procedure. I was told that if I left water in the tanks and the valves closed, the tanks and the valves could freeze and crack. But I had also read that it was bad to leave both valves open because the bacteria from the black tank can get into the gray tank, and I could be breathing it through venting in the sinks and shower.

Camping World
Shop Camping World Products on Sale Now!

Please help. It's a 1992 Europa, and the holding tanks themselves are supposed to be double-walled and insulated, so I don't think the tanks would crack.

ANSWER Hi Liz, I am sorry to hear you are going through this. Let's see if I can give you some suggestions on preventing this from happening in the future. Since you do not mention having any problems with the freshwater system in your RV, we will stick to solving the problem with the Black and Gray Water holding tanks. You mentioned that your holding tanks are supposed to be double-insulated and should not freeze. We will assume that they can freeze just to be on the safe side. Because if they do freeze and rupture, you are in a costly repair process.

I am assuming that you are hooked up to electric at your campsite and that you are running the furnace or using Space Heaters at night to keep some warmth in your RV. If your RV's interior temperature remains above freezing, you should not experience any freezing problems in the faucets or interior drains.

I am not
very keen on the idea of keeping the holding tank dump valves partially open to maintain a water flow going to the sewer, for the reasons you have mentioned above and because depending on how you have your sewer hose running from the RV to the sewer you could be setting yourself up for having an ice dam form in the sewer hose that could back up the gray and black water into the RV. I am not sure if that is what caused your most recent flood.

If I were you, I would keep the sewer hose stored away until you must use it to dump. Do not keep it hooked up all the time. The constant temperature variations could cause problems with the sewer hose, creating an even messier problem the next time you dump the tanks.

Good Sam Roadside Assistance
Over 1,500,000 successful roadside rescues—Good Sam RV Emergency Road Service

To prevent the gray and black water tanks from freezing you need to go out and buy some Non-Toxic RV Antifreeze which is designed for RV use. How much you will need depends on the size of your holding tanks. Once you get the antifreeze, empty the gray and black water tanks. Close the dump valves and store your Sewer Hose. Now add a couple of quarts of the antifreeze to your black tank through the toilet in your RV. Add another couple of quarts to your gray tank through the shower drain. This antifreeze will also prevent your dump valves from freezing and protect your shower drain if it happens to be in a non-insulated section of the RV.

Dump your tanks frequently, do not let them get above half full before dumping them. Remember, as the tanks start to fill up, you will need to keep adding more antifreeze so the antifreeze does not become too diluted. Once you dump the tanks, start the process all over again.

Some more permanent solutions to this problem would be to install a RV Tank Heater Pad to both holding tanks. A holding tank heater is like a large electric blanket that attaches to the bottom of the holding tank and depending on the make and model either plugs into a 120-volt outlet or runs off DC current and prevents the tank from freezing. Watch the video below to learn more about the Ultra Heat Holding Tank Heating System.

I hope that the suggestions that I have given you will help solve your holding tank problems.

Comments for How Do I Prevent My RV's Holding Tanks From Freezing During Winter?

Average Rating starstarstarstarstar

Click here to add your own comments

Heating Pads
by: Gritty Gray Goose

My tanks have a rough surface. The pictures and ‘how to’ videos show a smooth surface. I have a 1995 Europa. W
How would the heater pads adhere to a rough surface?

What about leaving the tanks empty
by: Anonymous

When in colder temps like this where freezing is a possibility, what about the idea of emptying your tanks and not using them? Not necessarily full-on winterizing as my situation is temporary. Are problems more likely to occur if you have empty tanks or partially filled tanks? Particularly for the black and grey tanks. I'm in a situation where I'm parked at someone's house and can use their plumbing, so I don't necessarily need mine. Would I be better off dumping the tanks and leaving them empty? Its getting down to the teens and '20s overnight and usually warms up into the 40s during the day. Thanks!

Winter RV Suggestions
by: Jim The Trucker

Excellent suggestion regarding RV antifreeze. I use a lot of it even in the fall and spring when I'm in the colder climates. It's cheaper at Walmart and don't be afraid to fill your freshwater tank, greywater and Blackwater tanks partially. Once you get into warmer weather you can flush everything out and you're good to go.
Be sure to run your pump until everything flows through pink like the color of the antifreeze. Then you'll know you're fully

IfIf I'mm camping in below-freezing temperatures I leave the doors open under my sink and bathroom vanity as well as the shower stall and my furnace keeps the inside temperature into the mid-to-upper 60s all night long.

How to live in travel trailer in freezing weather.
by: Anonymous

Heated Drinking Water Hose

I have had to live in a travel trailer while working in temps that were zero to -18 on a constant basis. Here is how I survived connected to shore power.

1. Get a powered, self warming water hose and you are good to - 30.

2. Shine a 500w shop light against the bottoms of your holding tanks. A 250W light did not put out enough heat to keep tanks from freezing. The 500W light allowed us to keep the tanks closed until full. I initially tried letting the grey water run out but the water froze in the drain hose.

3. Keep an area heater going as needed.

4. When showering, run a hair dryer to keep the bathroom warm.

5. Go south!

Modular home support
by: Earl

Holding Tank Heating Pads

Consult some one who uses heat tape to works on modular homes to protect your travel trailer waste systems.

Note from RVing Al: They do make Holding Tank Heating Pads (like the on pictured above) that are designed to prevent holding tanks from freezing

by: Matt

heat tape

I would never leave my valves open in the winter. (Northern Canada) get you some heat tape and do the valves up good, or build an insulated box around your valves and throw a 100W bulb in there. I've boondocked to -45C and sometimes it's best to go dry and keep a water jug in your trailer. However I doubt it gets cold enough where your at for the ice to creep up your valves.

Make an Insulated box around the tanks
by: Anonymous

We built an insulated "box" around our tanks using insulation board. Then we can put a heater in the area and thaw the valves. Here's the link to how we did it:

Insulating holding tanks
by: Pyrite

I have heated 12 volt holding tanks , bw and gray, but was advised that they would not be sufficient so I insulated the tanks. Ii used R5 , one inch rigid insulation, high end silicone adhesive. Cemented all the connections, then taped over all the joints, everywhere. I used gorilla tape with an overlay of foil back tape on top of the gorilla tape. I used an R5 foam , 2 inch 1/8 thick ., double layer over the drain lines, and foil tape covered the foam. for the discharge valves, I will make an insulated mitt . THINK IT WILL WORK?

Buy The Best RV Holding Tank Heater
by: UHI Worldwide

An RV Holding Heater, such as the UltraHeat will prevent your RV's Holding Tanks from Freezing During Winter. Check out our YouTube Channel to learn more about how your RV drainage system works, and how to prevent your RV Holding Tanks From Freezing During Winter Camping and Travel ...

Click here to add your own comments

Return to Ask an RV Question.