Freezing water is the single most expensive thing that happens to a parked camper. Water expands about 9% when it freezes, and it does not care what it is sitting inside — a pump housing, a low-point elbow, the copper on a water heater. A $12 blowout adapter prevents a repair bill that regularly runs past $1,500.
This guide covers both jobs, because they are not the same:
- Storing the camper — the goal is zero standing water anywhere in the system.
- Camping through the cold — the goal is the opposite: keep water moving and keep heat in.
When to do it
Winterize before the first hard freeze, not the first cold night. A hard freeze is roughly 28°F (-2°C) held for four or more hours — that is when water inside a trailer's plumbing actually reaches freezing, since the shell holds some heat. In most of the northern US that means late October; at altitude it can be late September. If you are unsure, do it early. There is no penalty for winterizing too soon.
Part 1 — Storing for winter
Step 1: Drain everything
Open the fresh water tank drain, both low-point drain lines, and the water heater. Pull the water heater drain plug or anode rod and let it run dry — a water heater holds six to ten gallons and is the most common freeze casualty. Open every faucet, including the outside shower, to break the vacuum so the lines actually empty.
Step 2: Blow out the lines
Draining alone leaves water trapped in every horizontal run. Connect an air compressor to the city water inlet through a blowout adapter, set the regulator to 40–50 PSI (never higher — you will split a fitting), and open each faucet one at a time, hot then cold, until only air comes out. Do not forget the toilet valve and the outside shower.
- RV Winterizing Kit with Pressure Gauge & 60" Hose — $31.20. The gauge is the point; guessing at pressure is how fittings crack.
- RV Winterize Blowout Adapter Kit — $12.00, brass with a ball valve.
- RV Blowout Plug 2-Pack — $16.00, lead-free.
Step 3: Antifreeze the traps
Blowing out the lines does not protect the P-traps or the toilet seal. Pour RV antifreeze (the pink propylene glycol kind — never automotive antifreeze) down every drain and into the toilet bowl. A cup or two per trap is enough. If you would rather push antifreeze through the whole system instead of blowing it out, bypass the water heater first or you will waste six gallons filling it. One exception: drains fitted with a self-sealing waterless valve hold no trap water at all, so they need no antifreeze — a HepvO waterless trap is a 15-minute swap that permanently removes a sink from this checklist (install guide).
Step 4: Batteries and seals
Lithium batteries should not be charged below freezing — most quality BMS units block it, but do not rely on that. Either pull the battery and store it somewhere above freezing at roughly 50% charge, or leave it installed with the system shut down. Walk the roof seams and window seals while you are at it; a small crack that leaks in November becomes delamination by March.
Step 5: Cover and skirt
A cover keeps UV, ice, and standing water off the roof. Skirting stops wind from stripping heat out from underneath, which matters even in storage if you have tanks or plumbing in the underbelly.
- RV Travel Trailer Cover 20–22ft, 7-Layer — $156.00, includes tire and jack covers.
- RV Skirting, Wind & Snow Proof, 36ft — $119.20.
Part 2 — Camping through the cold
If the camper stays in use, you are doing the opposite job: water needs to stay liquid. Everything below is about keeping heat where it belongs.
Tanks and sewer
Holding tanks freeze before supply lines do, because they sit exposed in the underbelly and hold standing water. Heater pads with a built-in thermostat only draw power when they need to.
- RV Tank Heater Pad 12×18", 3-Pack with Thermostat — $72.00.
- Heated RV Sewer Hose Cover, 14ft — $84.00, rated to -20°F.
The water hookup
A standard hose on a freezing night is a solid block of ice by morning. This is the most common cold-weather failure and the easiest to prevent.
- Heated RV Water Hose, 15ft — $72.00, rated to -45°F.
- Heat Tape for Water Pipes, 6ft — $26.40, to -40°F.
- Pipe Foam Insulation Wrap, 2" × 33ft — $15.92.
- Insulated Hose Bib Cover — $19.20, for the park spigot.
Keeping heat inside
Most heat leaves through the door, the windows, and the roof vents. These three fixes cost less than a tank of propane and pay for themselves in a week of cold nights.
- RV Insulated Door Cover, Magnetic Closure — $49.60.
- RV Vent / Skylight Insulator, 14×14" — $19.20.
- Thermal RV Window Cover, 2-Pack — $46.40.
The short checklist
- Drain fresh tank, low points, and water heater
- Blow lines out at 40–50 PSI, every faucet, hot and cold
- RV antifreeze in every P-trap and the toilet (waterless-trap fixtures skip this)
- Bypass the water heater if you are pumping antifreeze
- Battery out or system off; lithium never charges below freezing
- Inspect roof and window seals
- Cover and skirt
- Camping through winter? Tank pads, heated hose, insulated door
Everything in one place
The full Winterization collection has 40 products in stock — blowout kits, tank pads, heated hoses, skirting, covers, and insulation.
If you would rather not crawl under the trailer in November, our Seasonal Prep & Winterization Service ($183.20) covers the full drain, blowout, antifreeze, and seal inspection at our Upland, California facility.
Related: RV tankless water heater troubleshooting · Off-road camper maintenance checklist · HepvO waterless trap install guide · Why your RV sink smells like sewer