Winterizing Your RV
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Freeze damage is the single most expensive and preventable problem an RV owner faces. Water expands about nine percent when it freezes, and that force splits copper fittings, cracks the plastic body of your water pump, and ruptures the thin walls of your water heater and holding tanks. A repair bill that runs into four figures is entirely avoidable with an afternoon of work. If you store your rig anywhere that dips below freezing, winterizing is not optional.
Start by emptying everything that holds water. Drain the fresh water tank, then open the low-point drain lines, which are usually a pair of colored valves under the coach. Drain and flush the black and gray holding tanks at a dump station, and while you are there, add a little tank treatment so residue does not harden over the winter. Remove any inline water filter cartridge, because you never want antifreeze passing through it and you do not want it freezing and cracking either.
The water heater needs special attention. Never put RV antifreeze into a six or ten gallon water heater, because you would waste gallons of it. Instead, turn off the heater and let it cool completely, then relieve pressure by opening a hot tap. Remove the drain plug or anode rod and let the tank empty fully. Many rigs have a bypass valve near the heater that routes antifreeze around the tank later, so locate it now and set it to bypass. If you do not have a bypass kit installed, it is a cheap and worthwhile upgrade.
You have two methods to clear the lines: blowing them out with compressed air or pumping in antifreeze. The air method uses a blow-out plug at the city water inlet and a compressor set to around 40 psi, opening each faucet one at a time, hot and cold, until only air comes out. Many owners then follow with antifreeze anyway for full insurance. To pump antifreeze, use the correct nontoxic pink RV antifreeze rated for potable systems, never automotive antifreeze, which is poisonous. Install a water pump conversion kit or draw from a jug through the pump inlet.
With antifreeze feeding the pump, work through every fixture from nearest to farthest. Open each faucet, hot side then cold, until pink fluid flows steadily, then close it. Do not forget the shower, the outside shower if you have one, the toilet, and the kitchen sprayer. Pour a cup or two of antifreeze down each sink and shower drain and into the toilet to protect the P-traps and the seals in the black tank valve. Run the pump only briefly at the end to confirm pink fluid throughout.
Finish with the details that people forget. Bypass or remove any water filtration and the ice maker line if your fridge has one. Cap the exterior faucets, and note on a checklist exactly what you did so de-winterizing in spring is straightforward. When the weather warms, you will flush the system thoroughly with fresh water and sanitize it before drinking, but that is a job for another day. For now, a rig that is fully drained and protected will emerge from storage exactly as you left it, with no surprise cracks waiting to leak.