How to Winterize a Travel Trailer Before the First Freeze

Forty gallons of water can sit in a travel trailer all winter without doing a single thing. The forecast drops below freezing in the fall and nothing happens. Nothing happens in the cold months either. Then one warm afternoon in spring the owner flips the pump on and hears water running somewhere inside a wall.

That's what winterizing prevents, and it's a smaller job than the dread around it. Water expands about nine percent when it freezes. PEX tubing has a little give and usually survives. The fittings between the runs don't, and neither does the pump head, and neither does a water heater tank sitting full with nowhere to put the extra volume.

Paying a shop to do this is a completely reasonable call. If the trailer is stored an hour away, or your back has opinions about crawling under a bumper in the cold, book the appointment and don't feel bad about it.

For everybody else, this is a driveway afternoon. And most of the expensive mistakes here aren't skipped steps. They're the right steps in the wrong order.

A trailer is the short version of this job, and it's worth knowing why before you start. There's no engine to stabilize fuel in, no generator with its own carburetor to worry about, no chassis battery buried under a step, no coolant to have tested. Strip those out and what's left is water, propane, one battery, and the question of how a box sitting on its jacks behind a garage gets through five months alone. Fewer systems, though, means the water side is the whole job rather than most of it, and a trailer hides water in places a walkthrough won't show you.

When to Winterize a Travel Trailer, and What Freezing Actually Breaks

There's no date. The trigger is the first hard freeze in your own forecast, and how long it stays there.

One number won't tell you. A dip below freezing that lifts with the sun is a different threat from a freeze that sits for a day with wind behind it, and the same low on two different nights does different damage. Duration and wind matter more than the headline low, which is why an owner in Minnesota and an owner in Tennessee can read the same advice and need different answers.

Winterizing puts the trailer away. If you're planning to camp in it this winter you never winterize at all, and the job inverts into keeping water liquid instead of getting it out. That's winter RV camping prep, the opposite project with the opposite gear list.

An RV water system was built to be light and serviceable, not warm. The lines run through an underbelly, along the floor, behind panels, through spaces nothing was ever meant to heat. A motorhome at least has an engine bay that stays above ambient a while after a drive. A travel trailer on its jacks behind a garage has none of that. Once the sun is off it, it's the same temperature as the yard, straight through.

A split fitting makes no sound in January. It sits frozen shut all winter, doing nothing. You find it in April by ear, with the pump running and water going somewhere it shouldn't.

Antifreeze or Compressed Air: Two Ways to Winterize a Travel Trailer

Both work. For a first time, use antifreeze.

Non-toxic RV antifreeze is propylene glycol, it's pink, and it gets pumped through the system to displace the water. What you get from it is feedback. When pink comes out of a faucet, that line is done and you can see that it's done. Nothing else in this job gives you that.

Going the other way, blowing the water lines out with compressed air, uses no antifreeze and leaves nothing to flush in spring, which is genuinely nicer in April. It needs a compressor, a blow-out adapter that threads into the city water inlet, and discipline about pressure. Two major trailer builders publish 30 PSI as the ceiling, and the wording on one of them is that going over it can damage your plumbing. Past that you're pressure-testing your own fittings. Other sources put the ceiling higher, in the 35 to 50 range, so check what your own manufacturer says for your own trailer.

Air gives you no confirmation either. You're trusting you held every valve open long enough on a system you can't see. First time through, take the pink.

One rule with no exceptions: never automotive antifreeze. Every manufacturer procedure worth reading says so in about four words, and the toxicology is why. Automotive antifreeze is ethylene glycol, and the CDC's toxic substances registry records that swallowing it can cause serious illness or death, forming crystals that collect in the kidneys. This is a system you'll eventually drink from.

What You Need to Winterize a Travel Trailer

A short list, and you probably own half of it.

Non-toxic RV antifreeze, two to three gallons for most trailers and more if the runs are long or there's an outdoor kitchen. A socket or wrench for the water heater drain plug, which varies by model, so check before you're under the trailer guessing. A bucket. Gloves. And the manual, which is the easiest thing to skip and the one worth not skipping: valve locations move between model years, and five minutes with the diagram beats twenty with a flashlight.

Going the air route instead? Add a portable air compressor and a blow-out adapter.

While the manual's open, look at the roof. Winterizing is the back end of the season's maintenance, and a seam that's been weeping since August turns into ice that pries it wider in January. Our RV maintenance checklist covers what's worth checking while the ladder is already out.

How to Drain a Travel Trailer's Water System

Empty the holding tanks first, before anything on the fresh side gets touched.

Black tank, then gray, in that order so the gray water rinses the hose on its way out. Then close both valves and leave them closed. A valve left open is how you discover in spring that something has been slowly drying in there for five months. If you're not certain which tank is which, our RV plumbing primer sorts it out.

Then the fresh side. Drain the fresh water tank. Find the low point drains, usually a pair of caps or pull valves hanging below the floor, one hot and one cold, and open them. They stay open until everything has run out. Closing them again is a later step, and doing those two in the wrong order is how the antifreeze ends up on the ground.

Open every faucet, hot and cold, plus the shower. Air has to get in for water to get out.

Drain the water heater too, but release the pressure before the plug comes out. That's the one step in this job that can hurt you rather than cost you money, and it's worth doing slowly.

Then go find the outside water. Outdoor kitchen. Exterior shower wand. Washer hookups. Icemaker line. Toilet sprayer. Yours may have one the last trailer didn't, and anything with a fixture has a line running to it that holds water. These are the lines that strand people, because they're outside, they're out of sight, and nothing about the inside of the trailer reminds you they're there.

RV Water Heater Bypass: The Step That Saves the Most Antifreeze

Bypass the water heater before you pump anything, or the pump fills a six to ten gallon tank with antifreeze you paid for and then flush back out in spring.

Your bypass is a small loop of plumbing behind the water heater's interior access panel, usually behind a bed or under a dinette. The published procedures describe it the same way: turn the bypass valve on, and turn the input and output valves to the heater off. Configurations vary: one valve on some trailers, three on others, a factory single-lever setup on a few. Find yours before there's a jug of pink in your other hand.

Pull the pressure relief valve on top of the heater first and let the pressure out. The manufacturer procedures flag that one as an important safety warning, and it is one. Only then does the drain plug or anode rod come out. A tank still under pressure sends its contents through that hole with force, and if the heater has run at all that day, the water is hot enough to scald. Let it cool.

With the tank empty and the valves in the bypass position, the antifreeze routes around the heater instead of into it. That's the difference between two gallons and ten.

Pumping RV Antifreeze Through the Lines, Drains, and Traps

Close the low point drains. Do that before anything else. The pump doesn't check, and antifreeze sent into an open drain runs straight onto the ground until somebody notices the jug emptying faster than the faucets are turning pink.

With the drains closed and the heater bypassed, get the pump drawing from the antifreeze instead of the fresh tank. Plenty of trailers have a factory winterizing valve and a short siphon hose for exactly this. If yours doesn't, disconnect the pump's inlet line and run a hose from it into the jug. Prime it, then work the trailer one fixture at a time.

Kitchen hot, kitchen cold. Bathroom sink, both. Shower, both, plus the handheld wand. Toilet. Outdoor kitchen. Exterior shower. Each one runs until it goes pink, then off.

Pink is the confirmation, and it's worth being slow about, because a line that never ran pink never got treated.

The lines aren't the entire system, though. Every P-trap under every sink and in the shower pan still holds standing water after the plumbing is clear, because a trap is a U of water by design. The published instruction is about a quart of antifreeze down each drain and each P-trap, and a little left sitting in the toilet bowl. The bowl water isn't cosmetic. It's the seal that keeps sewer gas out, and an empty bowl in March smells like exactly what it is.

Tank valves stay closed. Pump off. Heater stays bypassed until spring.

Battery, Propane, and Five Months Parked

The water system is most of the job. What's left is short, and skipping it is how people open the door in April to a dead battery and a black bloom on the wall behind the mattress.

The battery is what people lose. A trailer parked with the battery still connected has a slow parasitic draw from the propane detector and the control boards, enough to flatten a lead-acid bank over a winter, and a flat battery that then sits frozen is a dead battery. Pull it and store it somewhere above freezing, or leave it in place on a smart battery maintainer that tops it up and then stops. Follow your manufacturer on which, because lithium and lead-acid want different treatment, and if the bank was already misbehaving before the cold, start with why an RV battery keeps dying.

Close the propane valves at the tanks. If you'd rather not find an empty bottle in the driveway on the first warm weekend, a propane tank level sensor reports what's in there from the house.

A sealed trailer with no airflow grows mold on the wall behind the mattress and inside the closet, and you find it in spring by smell before you find it by looking. Crack a vent if where it's parked allows for that, put a small dehumidifier or a moisture absorber inside, and check the roof and window seals now rather than in April. Rodents come through the underbelly openings and the gaps around utility runs, so look at where the wires and pipes enter and close what you reasonably can.

Covers divide people, and both camps have a point. A breathable cover made for the trailer keeps UV off the roof and sidewalls through months of low winter sun, and it stops leaves and needles from composting in the seams. A cheap tarp does the opposite: it traps moisture underneath, and in wind it works like sandpaper against the clearcoat all winter. If you cover it, the fit and the fabric are what decide whether you helped. If you don't, the roof and the seals become the thing you check first in spring.

Where it spends the winter matters as much as any of it. Our guide to where to store your RV trailer covers covered, indoor, and the open lot down the road.

Travel Trailer Winterizing Mistakes to Avoid

Four of them, and three are sequence.

The bypass left in the wrong position. Everything else goes right, pink comes out of every faucet, and the water heater quietly took six to ten gallons of it. You find out when you go back for a second case.

The low point drains left open. Antifreeze on the gravel, an empty jug, and a system you believe is treated.

The outdoor kitchen and the exterior shower. Outside, out of sight, and easy to forget from inside the trailer. A split line out there is a small repair and a large irritation, and it's the most common thing a first-timer misses.

Doing the entire job correctly and then labeling nothing. Somebody hooks the trailer to city water on a warm weekend to wash it and pushes municipal pressure into a system full of antifreeze and closed valves. Tape a note over the city water inlet. Future you is a different person with a worse memory.

Your Travel Trailer Winterizing Checklist

In order:

1. Empty the black tank, then the gray, and close both valves.
2. Drain the fresh water tank.
3. Open the low point drains and every faucet, hot and cold, and let it run out.
4. Release the water heater's pressure at the relief valve, let a hot tank cool, then pull the drain plug.
5. Set the water heater valves to bypass.
6. Close the low point drains.
7. Switch the pump to draw from the antifreeze.
8. Run every fixture until it goes pink: kitchen, bath, shower, toilet, outdoor kitchen, exterior shower.
9. Pour about a quart of antifreeze down each drain, and leave a little in the toilet bowl.
10. Pull or maintain the battery, and close the propane valves at the tanks.
11. Ventilate, add a moisture absorber, check the seals, close the rodent routes.
12. Tape a note over the city water inlet so nobody undoes all of it in March.

If this is the first season the trailer has been yours, our guide to towing a travel trailer covers the other half of the learning curve.

FAQs

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