Common questions if traveling or living in an RV during the winter include how to keep RV holding tanks from freezing and how to keep RV pipes from freezing while camping. Don’t have time to read this now? Pin it for later! We only recommend products we love and your support means a lot to us! This post contains affiliate links and if you make a purchase after clicking on our links we will receive compensation at no additional cost to you. UPDATED 3/16/2022

5 steps to keep RV pipes and holding tanks from freezing

Use a combination of these five steps:

1) Thermostat controlled personal space heater in the wet bay
2) Keep fresh water tank as full as possible
3) Add antifreeze as necessary to grey and black tanks
4) Consider adding a heated water hose
5) Keep sewer hose elevated off the ground

How to Keep RV Pipes from Freezing

Wet Bay Problems

Our wet bay where the grey/black drain valves, water pump, and water inlet lines are is a weak spot. The entire bottom of the bay is not well insulated and has little gaps and holes where cold air gets in. The fresh water tank is at the lowest point near the ground with the grey and black tanks stacked higher above it. Inside the bay are exposed water lines that feed the water pump and then from there go up into the motorhome plumbing.

We’ve found out the hard way those narrow plastic water lines can freeze quickly and then the next morning there is no running water for several hours until they thaw out. Our dump valves are also here so if they freeze up, we will not be able to empty out our grey and black tanks!

One final consideration is if the temperature is not going to be above freezing that next day, those pipes or drain valves will not thaw out without some assistance so get ready to break out a hair dryer! With a little pre-planning though, you can avoid this hassle.

Wet Bay Solution: Thermocube + 250 Watt Space Heater

Wet Bay Space Heater Setup. Click to enlarge.

Our solution:

Run an extension cord from another nearby storage bay that has a power outlet to the wet bay.
Attach a Thermocube to the cord.
Plug into the thermocube either a utility light (this one linked comes with 50-watt incandescent but you may want to put in a 100-watt bulb) or for really cold temperatures like single digits and lower use a 250-watt space heater.
- We went with the 2500 watt space heater.

The thermocube allows power to reach the space heater if a certain temperature threshold is reached, and then shut it off when a different threshold is exceeded. The one we use turns on at 35 degrees F and then off again at 45 degrees.

There are different models you can buy with different threshold configs. With this config, it’s fully automatic requiring no intervention on your part: the space heater comes on and off automatically when needed to keep the bay warm enough and this system has worked flawlessly for us. Above is a picture/diagram with labels.

Updated 3/16/2022: This thermocube solution continues to work amazing for us! We have had single-digit temperatures overnight and below-freezing weather during the day for multiple days in a row.

The Catch

The only catch is if your boondocking and running on batteries. That 250-watt space heater uses 21 amps per hour at 12V (watts = amps * volts). So with our 705AH house battery bank (352AH usable at 50% SoC) it would need charging after running this space heater only 16 hours [if it was the only device running. Granted the space heater only needs to come on a few hours overnight so it usually only uses a small portion of that, but it’s a big consumer of power relative to other appliances you might be running.

For example, our residential fridge needs half the energy and we can run both furnaces at the same time and still use less electricity than that one little heater. Electric heaters are just not very efficient. We usually have to run the generator for a couple hours in the morning in this case to get the battery bank back up to a 85% SoC.

How to Keep RV Holding Tanks from Freezing

Holding Tank Problems

Your RV has three holding tanks: 1) Fresh water 2) Grey (sinks + shower) and 3) Black (toilet) and they sit in the underbelly of your RV. In travel trailers and fifth wheels, they are often completely exposed down there to the elements. In our motorhome, they are accessible from the wet bay and are more protected in a the underbelly which is insulated. The contents could be prone to start freezing when the temperature drops below freezing for a longer period of time. For example, we noticed this recently when the temperature was in the teens for several days and nights in a row. Using our wet bay heating trick above, we were still able to dump problem free, but could tell the contents themselves were becoming slushy.

Holding Tank Solutions

You have a few options here:

Antifreeze - pour some of this in the grey and black tanks between dumps to keep the contents from freezing up. It goes without saying but do not put this in your fresh water tank!
Heated tank pads - found standard on some RVs like higher end motorhomes but with some RVs, you could install them later. Our Phaeton does not have them, but we have not yet been in a situation where they were needed. Our wet bay solution above and/or antifreeze has prevented any problems.
Skirting - if your holding tanks are not in an insulated area, this is an effective method as it reduces the amount heat from escaping through the underbelly by blocking cold air and wind from reaching there. There are numerous materials and attachment methods to accomplish this that I won’t go into here, but we’ve even see people just shovel snow into piles around the perimeter of their RV. Snow is a great insulator believe it or not.
Dump tanks wisely - Keep both valves closed and only dump when your tanks are full to reduce the risk of freezing.
- We still leave the sewer hose hooked up but elevated off the ground on a sewer hose support.
Keep the tanks empty / winterizing - I’ll mention it, but it’s not really an option especially if you are full timing. We personally like to still have use of the faucets, toilet, and shower.

RV Water Tank Freeze Protection

To combat the RV fresh water tank freezing, we keep our fresh water tank as full as possible because it’s more difficult to freeze up a large quantity of water vs a small quantity.
Don’t leave your water hose attached to an enabled city water connection or else the hose and the water contents will freeze solid.
Alternatively, you can get a heated water hose if that’s too much trouble. They come in 12, 25 and 50 foot lengths.
We use an app called Dark Sky to send us an alert if the overnight temp is going to drop below freezing so we can make sure the water hose is safely stored and the fresh tank filled.
If you forgot to do any of the above and your external hoses freeze up, use a hairdryer to soften them up and thaw the contents.

Conclusion

We recommend a combination of these five steps: 1) Thermostat controlled personal space heater in the wet bay, 2) Keep fresh water tank as full as possible, 3) Add antifreeze as necessary to grey and black tanks, 4) Consider adding a heated water hose, and 5) Keep sewer hose elevated off the ground, to keep RV pipes and holding tanks from freezing. Get the recommended parts for Amazon with our links below.

Looking for other winter RV living tips? Check out our chart in our How to keep your RV warm in winter article which details the different heat sources you can use depending on whether you are plugged into shore power or boondocking using your generator. Take a look at our Cold Weather Amazon Favorites article for our list of Amazon gadgets that make the cold weather a little more manageable.

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