How To Keep Rv Water Tank From Freezing

Winter RV Camping has different and new challenges. Keeping the RV water tank from freezing is the primary one. The most common concerns are will my water freeze and my holding tanks freeze in my RV when I am winter camping?

There are three primary tanks on the bottom of most Self Contained RVs, (Self Contained RV is defined as having full requirements for living including bathroom and kitchen and their normally featured conveniences.) There is a typical small 6 gallon water heater tank too. The three large tanks on the bottom of the RV are:

  1. RV Fresh Water Tank – Drinking water reservoir used when not hooked up to water facilities at the RV Site.
  2. RV Grey Water Tank – This accepts water from the kitchen and bathroom sinks and shower drain.
  3. RV Black Water Tank – This RV Sewer tank receives the toilet.

There is a water heater tank too, not located on the bottom, typically about 6 gallons.

These top three tanks are fairly large, and can be seen mounted to the bottom of the RV when you look underneath. This is the first clue. Is my RV a Four Season RV?

Ideally it would be nice to get the Four Season RV in all cases, so you are prepared. A four season RV has tank heaters, and are in an insulated area under your RV.

In reality, the tanks are exposed, and most RVs are not four season RVs. Most all RVs are made with an insulated floor now, but the tanks are typically built underneath, totally exposed to the outside temperature. The challenge is to keep the RV water tank from freezing in the winter.

How to Keep RV Fresh Water Tank from Freezing

For the RV Potable Drinking Water tank, the valve is a small one, typically a small outlet with a small “petcock” valve that you turn 90 degrees, and open to drain. There are two drinking water sources, one is this tank. This tank is your first water source choice, and if all works well, when you turn the water on and the pump switch is on, it will “start upon pressure demand” meaning the pressure is released by opening a faucet, and the pump works to regain pressure, or allowing the release your tank of drinking water for you to use.

The second fresh water source is called City Water or Municipal Water, commonly your full hook up water source. This is the faucet at the RV Park.

When you are hooked up to the full hook up water source in the RV Park and a hose is attached, this provides the pressure you need and the supply of water you need. The portable water tank pump should be in the OFF position, so that the water pressure is satisfied with the full hook up faucet and the pressure from that water source.

With your water hooked up to an external source, and the tank pump switch in the off position, this basically disconnects your potable water system from being required. Water is supplied from the outside, so now we need to keep it from freezing.

Simply open the petcock drain typically located on the drivers side behind the back wheels, a bracket that holds the petcock valve and small hose opening. Most RVs and Travel Trailers mark it well quoting it as “Potable Drinking Water Drain”. The fill component is up high and looks like a hose fitting.

This should be kept shut to keep contaminates out. The drain is under the RV, and will be the lowest point of the water drain, so that it all drains out.

Drain tip. “Open while traveling, so that the rocking motion of travel allows all of the water to exit. With no water in the tank there is nothing to freeze. The tank itself will become somewhat brittle as lower temperatures does that to materials, so be careful as to not impact the plastic tanks in any way.”

Once the potable water tank is fully drained, and you are hooked up to the external full hook up potable water supply outside, then the tank should not be able to freeze and you are done with the freezing concern on this first water tank.

Then you can start on the hose tape and hose system, providing thermostat controlled tape element that you can tape to your white potable water hose, (white hose is considered safe for drinking water), as well as your water hose filter and RV Park faucet, all the way down to the ground.

Keeping all of the RV the water supply controlled with electric tape attached and plugged in, with insulation wrap around the hose, are designed to keep it above 40 degrees and prevent freezing.

How to Keep RV Gray Water Tanks from Freezing

For RV Gray Water Tanks, we keep them open. Your RV park will tell you what they recommend, (using their full hook up during the winter), as they know what works in their area. With open tanks, there is no accumulation of liquids, so prevents the small amounts to travel to the drain with minimal water residue to freeze.

The Grey water tank will accept non salted, basically clean water, so does have the most opportunity to freeze. With a very short Sewer line, parking the RV as close to the sewer source as possible, and a sewer ladder that ramps the sewer pipe to the ground opening, the water should roll on out as you use it, and not be in an above ground storage situation so is a good way to prevent RV Gray water tanks from freezing.

Warm water can be used to help melt any residue in your tanks, but might caution against using full hot. The thermal shock of hot water to a tank might cause concern in an older tank.

Most tanks should be made to handle it. A warm shower typically would clear out the Gray Water tank from any built up ice residue. Normal use should of water usage, warm water for dishes with dish soap, as well as warm showers should keep it clear.

If you have a concern, a small amount of RV Pink antifreeze could be used, but so far we are doing fine without it. With the valve open, the antifreeze will drain on out anyway. It might permeate any ice that accumulates in the bottom of the drains, but again is nothing we have to do.

Note, do not drip water!!! The dripping might make water accumulate in the sewer side of the tanks, and start ice build up. The RV Black water tank will help keep the lines clear below the point where Gray water and Black water come together in the pipe.

How to Keep RV Black Water Tank from Freezing

The black water tank is not any concern as long as the RV is warm and the water in the toilet is at room temp, and the lines going to the toilet do not freeze. The water lines for toilet and Black Water flush are all inside the RV, so with normal winter camping use, should be fine.

The black water tank itself accepts, (without too much elaboration), a very salty concentration of liquids, and a volatile compound of gasses in solids, so do not have much of a chance of freezing in normal conditions, especially in an immediately fully drain-able situation.

With it rolling down hill and the Black Water Tank valve left open, all will roll to the ground opening in due course, without the chance of freezing along the way. With the amount of salt in the fluids alone, the Black Water Tank would be the last of your concerns of the three tanks.

With the gray water tank and black water tank coming together at the junction, these volatile components of our refuse should keep the drain pipe melted and no ice of any measurable consequence should accumulate.

We do flush the toilet with fresh water pretty frequently, but again with no dripping to allow ice accumulation.


To keep the entire RV water tank from freezing:

  • Skirting and using a bulb for heat under RV.
  • Wrapping sewer and water pipes with heat tape to prevent RV water and sewer lines from freezing in cold weather.
  • Lastly, the water heater if switched on electric or gas, should keep the RV water tank from freezing, and keep your hot water running.

Note: problems might vary with Age of RV, condition, as well as different factory recommendations. We are only quoting what works for us, Full Time Winter RVers. No warranties are implied with any statements, at your own risk, of course.

With freezing, wind direction, shade or sun throughout the day, temperature ranges, as well as freezing duration of weeks versus just nights will make a big difference. Attention to these things might allow sun to hit your water and sewer supply lines at least once a day to help this.

Wind can drop the temperature of an item just by wind exposure, so blocking or positioning to avoid that cold windy side might help. Shielding the hose or sewer line might help if again the wind is apparently intense.

Overnight freezes are short term, and sun can thaw by the time you make your first pot of coffee if it does freeze.

Long term freezes however will test your method and allow ice build up over time. If your system works as possibly outlined above, then it should stay thawed under most conditions barring serious “north mountain face type” extreme situations.

In summary, our suggestions (no warranties or assurances implied), keep all tank valves wide open to drain on out, including Potable water tank, Grey water tank, and Black Water Tank.

Keep your water heater ON for the water heater tank, as normally used, and use the water supply electric tape to keep water supply hose to 40 degrees at minimum, and put the insulation tube or wrap around the entire water hose and water source (all the way to the ground) and plugged in, keeping the water line coming in to the RV at 40 degrees or better.

If you expect to be somewhere during long freezes as well as long term, Skirting your RV is highly recommended to keep the RV water tank from freezing. The skirting allows the use of a light bulb that puts off heat, and can be located under tanks and valves to keep them running.

I am John Morris. I have been a car enthusiast since I was 15, when I acquired my first Ram 1500. Follow me on this fascinating journey through this website with shared tips, guides, insights, and more.