How to winterize RV plumbing: The complete guide

• 2 to 3 gallons of RV antifreeze for a typical travel trailer, more for large fifth wheels and motorhomes with extra loops. Only non-toxic RV antifreeze, propylene glycol, never automotive antifreeze, which uses poison ethylene glycol.
• A water pump winterizing kit, the valve and hose that let the pump draw from a jug instead of the fresh tank. Kits are inexpensive and worth adding if yours does not have one.
• A screwdriver for access panels, and a 1-1/16 inch socket for the water heater drain plug on most models.
• For the air method: an air compressor, a blow-out plug for the city water inlet, and eye and ear protection.

Where to get the gear. These are the maker's own product pages: Camco RV antifreeze, the Camco pump converter winterization kit, and the Camco blow-out plug. Other brands work fine; the important part is the label, RV and marine antifreeze, never automotive.

Antifreeze only protects what it reaches. Every drop of water left in a line, a tank, or a pump is a potential ice pocket, so the draining step is the foundation of everything that follows. Give it the time it deserves; a hurried drain is how lines crack.

Drain the fresh water tank

Open the fresh tank drain valve and let it empty completely. Prop the valve open while you work so any remaining water keeps dripping out.

Open the low-point drains

Underneath the RV, usually near the centerline, you will find one or two low-point drain valves or caps, one for the hot line and one for the cold. They are often colored or labeled, red for hot and blue for cold. Open both. A single low-point drain left closed holds enough water to cause line damage overnight, and it is exactly the kind of crack you will not find until spring.

Run every faucet to let air in

Open both sides of every faucet, plus the outdoor shower if you have one, so air can enter the lines and water can leave them. Flush the toilet until the bowl is dry. Leave everything open while you work so the system keeps draining.

Turn it off and drain the tank

Turn off the water heater on both gas and electric. Let the water cool, then open the pressure relief valve so air can enter the tank. Remove the drain plug at the bottom, on the exterior access panel, and let the tank drain completely, which takes several minutes for a 6 or 10 gallon tank. Open a hot faucet inside as you drain so the lines behind it empty too.

Anode rod or drain plug: Know which you have

The plug in the bottom of the water heater depends on the brand. Suburban water heaters use a steel tank with a sacrificial anode rod. The rod is 9 inches of metal that protects the tank by corroding in its place, and the hex head on the drain plug is the anode. While it is out, inspect how much rod remains. Atwood and Dometic heaters use an aluminum tank with a simple plastic drain plug and no anode rod. Do not install an aftermarket anode rod in an Atwood aluminum tank; the metal reaction can seize it in the threads. Whichever brand you have, if any part of the rod or plug looks badly consumed, replace it now with the proper part for your heater.

Set the bypass valves

Behind the water heater, often under a removable panel, are the bypass valves, most RVs use a one or three valve setup. Their job is to route water around the heater instead of through it. On a three valve system, the common arrangement is the inlet and outlet valves closed and the center bypass open. On a single valve system there is one handle, and turning it diverts the flow away from the tank so the heater stays dry: the positions are molded or labeled on the valve body, and if they are not, the owner's manual for your water heater is where that layout is drawn. Getting this step wrong either fills the tank with antifreeze or leaves water in it, and both are expensive. Turn the handles perpendicular to the pipes to close, parallel to route flow. Confirm the bypass by tracing both the hot and cold feed lines visually. If antifreeze later flows into the tank, the bypass was not fully set, and you will waste several gallons trying to make pink show at the faucets.

Leave the plug out or loosely in place until spring. The tank must stay empty. If you are storing outdoors, the plug can go back in loosely or the opening can be screened so nothing crawls in while still letting the tank breathe and stay dry.

How to winterize with RV antifreeze

RV antifreeze is propylene glycol, formulated for drinking water systems and safe for the pipes. It protects by replacing the water in the lines with liquid that will not freeze, so even a missed pocket of moisture is diluted into a mix that survives. The method has two ways to feed the system.

The pump winterizing kit, preferred: find the water pump, where the suction line normally draws from the fresh tank. Switch the diverter or attach the siphon hose so the pump draws from a hose dropped into the antifreeze jug instead. This is the clean way and uses the least antifreeze, and if your pump does not already have the valve, a pump converter winterization kit adds one in minutes.

Pouring into the fresh tank, the fallback: drain the tank first, leave the drain closed, pour two to four gallons of antifreeze into the tank, and pump it through from there. It works, but it takes more antifreeze and leaves the tank itself full of pink, which must be flushed in spring.

Method at the faucets: start at the faucet farthest from the pump and work inward. Turn on the pump, open the cold side until pink runs steadily, close it, open the hot side until pink runs, close it, and move to the next fixture. Cover every faucet, the shower head, the outdoor shower, the toilet flush until pink appears in the bowl, and any washing machine or ice maker connection your RV has.

How to blow out RV water lines with compressed air

A compressor blows the water out of the lines with air, leaving the system dry instead of filled. It is faster and leaves no pink taste to flush in spring, but it has to be done thoroughly, because a single trapped pocket of water is still water, and it will still freeze.

The settings that matter: screw a blow-out plug into the city water inlet, connect the compressor, and set it to the pressure your own manual specifies. Two makers bracket the range and they do not agree: Jayco caps its system at 30 psi and warns that exceeding it can rupture line couplings and void the warranty, while Winnebago publishes 35 to 50 psi and says anything higher may damage the plumbing. If you cannot get to your manual, start at 30 psi and do not go higher until somebody confirms your system is rated for it: that is the conservative end of both makers' ranges. Read your manual, because the ceiling is the plumbing's, not the compressor's. Work one valve at a time, opening each faucet until it spits only air, and repeat around the whole RV, including the shower and toilet valve. Wear eye and ear protection; a blowing line is loud. When the air runs clear, close everything and disconnect.

Use both for the best result. Blowing the lines out first and then running antifreeze through them protects the plumbing two ways: the air removes the bulk of the water, and the antifreeze covers whatever the air missed. It uses less antifreeze than the antifreeze-only method and adds a second layer of certainty.

Protect the P-traps: Pour antifreeze down every drain

The sink and shower drains do not connect to the pressurized lines you just protected, and the water sitting in their curved P-traps is exactly what freezes and cracks first. Pour about a cup of antifreeze down the kitchen sink, the bathroom sink, the shower drain, and any floor drain, so the traps hold pink instead of water. Skip this step and it is the one that produces the mysterious bathroom-sink crack in spring.

Remove the inline water filter

A filter full of water will freeze and split its housing. Remove the cartridge, store it inside the RV, and cap or open the filter housing so nothing holds water.

Dump the black and gray tanks

Empty both waste tanks completely, at a dump station or approved drain. Water left in the bottom of a holding tank can freeze and warp the tank or crack the valve. Then put RV antifreeze in each tank and leave the dump valves closed, with the discharge cap on. Closed is the common practice, and it keeps the antifreeze in contact with the seals with the outlet shut. Not every maker agrees. Drain Master, which builds waste valves, tells owners to store the blades open so the seals sit relaxed rather than pressed against the gate, which it says invites stiction, and Airstream's own winterizing guide has owners leave the dump valves open. Closed with antifreeze is the safer default; if you do leave a valve open, keep the cap on and the system dosed, because an open valve with the cap off or worked loose is a way in for insects and rodents.

Protect the wet bay

If your RV has a heated wet bay, clean the strainers and confirm the heater works before you need it. If the bay is not heated, insulate the compartment and, on cold nights, use a small heater or a 60-watt incandescent bulb, but only if the setup is safe to leave unattended. Winterizing the whole bay is the safer answer where the plumbing sits in it.

Undoing winter is easier than doing it, but the order still matters. Sanitize the fresh system first, then flush the pink out, then restore the water heater.

• Close the low-point drains and reinstall the water heater plug or anode rod, torqued properly with the correct part.
• Put the bypass valves back to normal operation: inlet and outlet open, center bypass closed. Confirm the water heater can fill before you energize it.
• Sanitize the fresh water system. The standard dose is a quarter cup of plain unscented household bleach to every 15 gallons of tank capacity, which lands at about 50 parts per million, the concentration the makers publish. Most makers also publish a doubled dose, half a cup per 15 gallons at about 100 parts per million, which is allowed to stand for just one hour if you want the job done faster. Go no further than that for a routine sanitize: the makers stop at 100 parts per million, and stronger concentrations raise the risk to the lines, seals and tank. The sulfur treatment below is the one published exception. A commercial sanitizer works too, at the ratio on its label. Run it through every faucet, let it sit, then drain and rinse until the bleach smell is gone.
• If the hot water smells of sulfur, that is a different treatment with a different number. Suburban publishes a heavy chlorination for the rotten-egg smell in a water system: about six ounces of household bleach to every 10 gallons in the tank, run through the system and left to sit for a few days. That is roughly four to five times the sanitizing dose above, and it is a remedy for a specific problem rather than the routine spring sanitize. Use it for that, flush thoroughly afterwards, and do not treat it as the everyday ratio.
• Flush every line until the pink is gone. Run fresh water through each faucet, both hot and cold, until it runs clear, and taste-test the kitchen cold line before anyone drinks from it.
• Fill and test the water heater last. With the bypass restored, open a hot faucet until water flows steadily, then turn on the heater. Never energize the electric element on an empty tank; it burns out in seconds.