The Call I Get Every Spring
Every March, without fail, I start getting the same calls. The owner stored the RV in October, everything seemed fine, and now they're opening it up for the season and something is wrong. Cracked pipes. A ruined water heater. A dead battery that won't hold a charge.
Here's what a spring call looks like in the field: a travel trailer came in with a water heater that had cracked over the winter. The owner had drained the water lines and thought they were done. They never bypassed the water heater. Six gallons of water sat in that tank through three months of freezing temperatures. When the tank cracked, the repair was $400 to $600 including parts and labor. The bypass that would have prevented it takes about two minutes and costs nothing.
That's the pattern. The mistake is small. The repair bill is not. These three mistakes come up more than anything else I see. If you're winterizing this fall, read this first.
Mistake #1: Skipping the Water Heater Bypass
This is the most expensive mistake on this list. It comes in two versions.
Version one: The owner pumps antifreeze through the entire water system without bypassing the water heater first. The antifreeze fills the tank completely. That's 6 to 10 gallons of antifreeze wasted on protecting a tank that just needed to be isolated. Most RV antifreeze runs $4 to $6 a gallon. That's $24 to $60 in antifreeze that served no purpose.
Version two: The owner drains the lines but never touches the water heater at all. Some water stays in the tank. Temperatures drop. The water expands. The tank cracks.
This is not optional. Before you touch the anode rod or drain plug, turn the water heater off completely — gas switch off, electric switch off. Then open a hot water faucet inside the RV to relieve line pressure. Removing a drain plug from a hot, pressurized tank is a serious burn hazard. Let the water cool first. This step cannot be skipped.
Not Bypassing the Water Heater
The water heater bypass uses two or three manual shutoff valves to route water around the tank during winterization. When the bypass is set, antifreeze flows through the rest of your water system without entering the tank at all. The tank stays empty and dry. Frozen water can't crack a dry tank.
Most RVs built in the last 15 years came with a water heater bypass installed. The valves are usually located behind the water heater access panel or inside a nearby cabinet. If yours doesn't have one, they're inexpensive to add and worth every dollar.
Before you start any winterization, locate the bypass valves and set them first. Every other step follows after that.
Leaving the water heater bypassed after winterization is the most common de-winterization error. If you turn on the water heater before opening the bypass, you're running an empty tank under heat. That damages the heating element and can void your warranty. Reset the bypass valves before you turn anything on in spring.
Mistake #2: Using the Wrong Antifreeze
The antifreeze you use in your RV's water system and the antifreeze you use in your vehicle's engine are not the same thing. They are not interchangeable. Using the wrong one can contaminate your entire water system.
Automotive antifreeze is ethylene glycol-based. It is toxic. It should never enter a freshwater plumbing system. RV antifreeze is propylene glycol-based, non-toxic, and rated specifically for potable water systems. It's the pink liquid you see at every RV supply store in the fall.
Using Automotive Antifreeze Instead of RV Antifreeze
You need non-toxic RV antifreeze only. Check the label before you buy. It should say "RV and marine" antifreeze and "non-toxic." The color is pink. If the label doesn't say non-toxic explicitly, don't use it in your water system.
The other common mistake is underbuying. Most rigs need 2 to 3 gallons for a basic water system with a bypass kit installed. If you skip the bypass, you'll need significantly more because the water heater tank adds 6 to 10 gallons of volume. Buy enough to push antifreeze through every fixture, including the toilet and any exterior outlets.
When pumping antifreeze through the system, start from the fixture farthest from the pump and work your way back. This pushes air pockets out ahead of the antifreeze and ensures every line gets covered. Run each faucet until you see pink, then move to the next one.
One more thing: remove any inline water filters before you start. Pumping antifreeze through a cartridge filter wastes the filter and doesn't protect it. Pull the cartridge out and bypass the filter housing during winterization.
Mistake #3: Leaving the Battery to Die
This one costs owners $100 to $300 and it happens because they don't realize a battery can freeze.
A fully charged lead-acid battery freezes at approximately -76°F. A fully discharged battery freezes at 32°F. That's a dramatic difference. A battery sitting at 50% charge over a cold winter in most of the country is in real danger. When a battery freezes, the cells crack internally. The battery will never charge properly again and usually needs to be replaced entirely.
Storing the Battery Without a Charge Plan
Before you store the RV for winter, bring the battery to a full charge. A fully charged battery can handle most winter storage conditions in most climates. Then you have two options: disconnect it and store it somewhere with stable temperatures (a garage is ideal), or leave it connected to a battery maintainer that keeps it topped off without overcharging.
If you leave it connected to shore power, that alone won't maintain the charge safely unless your converter has a proper multi-stage charging mode. A simple battery maintainer plugged in at the storage site is the most reliable solution.
| Battery State at Storage | Freeze Risk | Recommendation |
|---|---|---|
| Fully charged (12.6V+) | LOW | Safe to store; use a maintainer for long storage |
| Partially charged (12.0–12.5V) | MODERATE | Charge fully before storing or use a maintainer |
| Discharged (below 12.0V) | HIGH | Charge immediately — do not store in this condition |
The Mistakes Nobody Warns You About
Most winterization guides cover the water system and stop there. Here's what gets skipped.
💧 Turning Off the Water Is Not Winterization
Every spring I get calls from owners who are certain they winterized — they turned off the water, maybe drained a tank, called it done. Then they open up in March and find split pipes, cracked fittings, and a destroyed water heater.
Turning off the water supply to the RV does nothing for the water already sitting inside it. Every pipe, valve, fitting, toilet supply line, and appliance in your RV is still holding water after you shut the supply off. That water stays right where it is all winter. When temperatures drop hard enough, it freezes. When water freezes, it expands. When it expands inside a rigid pipe or tank, something cracks.
Winterization means removing the water from the system entirely — either by blowing it out, pumping antifreeze through, or both. Turning off the supply is the first step of nothing.
If you have a tankless water heater, pay close attention here. I see cracked tankless units constantly. The internal heat exchangers are built from thin brass and copper tubing — they have very little material between the water inside and the freezing air outside. A standard tank-type heater has some mass to it. A tankless unit does not. The thin-walled components fail the moment the water inside them freezes, and the damage is usually not repairable — you're replacing the unit.
If you have a tankless heater, draining it per the manufacturer's exact procedure AND running antifreeze through the system is not optional. The specific winterization steps for tankless units differ from tank-type heaters — confirm the correct procedure for your unit before you start.
🚿 The P-Traps Under Every Drain
Every sink, shower, and floor drain in your RV has a P-trap, which holds a small amount of water to block sewer gases. You can blow out the main water lines all day long and never clear those traps. They hold water by design.
After you've pumped antifreeze through the water system, pour a small amount directly down every drain. Sinks, shower, floor drain, outside shower. This fills the P-trap with antifreeze instead of water. An unprotected P-trap can crack in hard freezes and require plumbing repairs in spring.
🛞 Tires Under Storage Load
An RV sitting on the same spot of pavement or gravel for months puts a flat spot on the tire at the contact point. Before you park it for the winter, check tire pressure and inflate to the correct cold inflation pressure per the manufacturer's specifications. UV exposure during storage also degrades sidewalls — tire covers help reduce that damage on units stored outdoors.
Write down what you did and when. If you completed a full antifreeze winterization, note the date. If you bypassed the water heater, mark it somewhere visible so you don't forget to reset it. A note on the water heater control panel is the most reliable reminder. Future-you will appreciate it.
When to Stop and Call a Tech
DIY winterization is straightforward if your RV has a standard water system. But there are situations where calling a certified technician is the right move.
"I've been doing spring startups for years. The calls I dread most are the ones where someone spent two hours doing it themselves, thought they were done, and opened up in March to find a crack they could have prevented. Winterization isn't complicated — but the details matter. Miss one step and that's the one that bites you."
The complete step-by-step winterization process is in the companion article: The Complete RV Winterization Checklist. It walks through every step in order, including the bypass, the antifreeze sequence, the battery, and everything else covered here.
It's quicker and less expensive to winterize correctly now than to pay for freeze damage in spring.