How to Winterize an RV Water System by Rig Type

If your RV will sit through freezing weather, the water system needs to be emptied or protected. SHURflo warns that frozen water can seriously damage the plumbing and the pump. The right method depends on your rig: whether you have a water heater bypass, and what kind of heater you own. This guide covers the water system only, as of October 2026. Your owner’s manual and the pump and water heater manuals come first. If they disagree with this page, follow them.

Which winterizing method fits your rig?

Start here. The steps below come from the manufacturer pages we read, listed under Sources. Your own manual may differ.

Do you have a tankless or on-demand heater, such as a Truma Combi or AquaGo? Yes: go to the tankless section. Truma says it does not recommend high-pressure air or antifreeze solutions for the Combi. No: continue.
Does your tank-style water heater have a bypass (valves or a kit)? Yes: Option A (antifreeze) or Option B (compressed air) can work. No: stop. Without a bypass, antifreeze fills the heater tank. Check your manual or ask a service center before you pour anything.
For Option B, does your manual give an air pressure limit? Yes: use that number, not a number from a video or forum. No: use Option A, or have a technician do the air blow-out. (Keystone’s guide gives a limit for its own rigs; see Option B.)

Method versus rig

Method	Fits best	Main risk	Where to look in your manuals
Drain-down only	Any rig, always the first step	Low points missed, water left in the pump	Owner’s manual winterizing section; pump manual
A: Antifreeze through the pump	Tank-style heater with a working bypass	Wrong antifreeze type; heater filled because bypass is missing	Owner’s manual; water heater manual
B: Compressed air	Rigs whose manual gives an air pressure limit	Too much pressure damages plumbing; traps and toilet seals stay unprotected	Owner’s manual (pressure limit)
Tankless drain and bypass	Truma Combi, AquaGo and similar	Using antifreeze or high-pressure air against the maker’s advice	Heater manual; Truma winterizing instructions

What you need before you start

Gather this first so you do not stop halfway with an open system.

Your owner’s manual, pump manual and water heater manual (or the maker’s winterizing page)
Non-toxic antifreeze made for potable water systems (Option A)
A bypass hose or kit for the pump’s suction side (Option A). Keystone’s guide describes a hose on the suction side connected to the antifreeze container.
A container for draining; Truma specifies one that holds at least 2.64 gallons (10 liters) for the Combi
The tool for your water heater drain plug (check your manual)
An air regulator and fittings, only if your manual allows Option B

Drain-down first: tanks, heater and low points

Every method starts with draining.

Turn off the pump or the city water supply. Truma’s Combi steps also say to open every hot and cold tap to relieve pressure.
Let the water heater cool. Dometic’s heater manual says to turn the heater off and allow time for the water to cool before removing the drain plug. Hot water can scald.
Drain the water heater tank. Dometic says to drain the heater before storing the RV for the winter or when freezing is possible. Remove the drain plug. If water only trickles, Dometic suggests opening the pressure-temperature relief valve to let air in, and clearing the drain opening with a small gauge wire.
Expect some water to stay behind. Because of where the plug sits, Dometic says about two quarts remain, and that this amount will not damage the tank if it freezes. That statement is from a 10-gallon gas-electric Dometic manual (revision A, 10/11/18). Other models differ, so check yours. Dometic’s steps end with replacing the drain plug and closing the pressure-temperature relief valve.
Open the low point drains and every faucet, hot and cold. Keystone’s guide says to remove the low point drain caps on the water lines.
Drain the pump. Pentair-SHURflo says the best protection is to drain the pump completely, then turn the pump power off once the plumbing is empty.

For heater problems, such as a unit that will not light, see our guide to an RV water heater that is not working. That article also covers draining for upkeep, so we do not repeat it here.

Option A: antifreeze through the pump

Use this when your tank-style heater has a bypass.

In normal mode, the inlet and outlet valves are open and the bypass valve is closed, so water flows through the heater tank. In bypass mode, the inlet and outlet valves are closed and the bypass valve is open, so water goes around the tank. Valve layout and positions vary by model. Check your manual.

Bypass the water heater. Keystone says to turn the bypass valves to the bypass position, and notes they are typically on the water lines entering the back of the heater. Valve layouts differ by model, so confirm in your manual.
Remove the water filter cartridge if your RV has one. Keystone says to remove and discard the cartridge and drain the housing.
Close the system again. Keystone says to reinstall the low point drain caps and close any open faucets and valves before pumping antifreeze. If they stay open, the antifreeze runs out of the drains.
Connect the pump suction hose to the antifreeze container (Keystone describes this setup).
Run the pump and open each faucet one at a time, cold side then hot side, until antifreeze comes out. Keystone also includes the outside shower and kitchen.
Skip the ice maker on a residential fridge. Keystone says not to add antifreeze to a residential refrigerator’s ice maker line. Drain that line with the other water lines instead.
Protect the drains. Keystone says to pour about one quart of RV antifreeze into each drain and P-trap, and the toilet. SHURflo also says potable antifreeze may be poured down drains and toilets to protect p-traps and toilet seals.

Use the right antifreeze. SHURflo states: “Do not use automotive antifreeze to winterize potable water systems,” and calls such solutions highly toxic. Keystone says automotive antifreeze is poisonous. SHURflo says non-toxic antifreeze for potable water is safe for use with its pumps. Check the label for “potable” or “non-toxic” and for use with RV plumbing.

Option B: compressed air

Some owners blow the lines out with air instead of running antifreeze. Of the maker pages we read, only Keystone’s compressed-air guide gives a number: connect the air hose to the city water fill with an adaptor and set the pressure to no more than 30 PSI. That figure is Keystone’s, for Keystone rigs. The SHURflo, Dometic and Truma pages we read do not give one.

What to do:

Look for the limit in your own owner’s manual. If your rig is not a Keystone and your manual gives no number, do not guess. Choose Option A or ask a service center.
Too much pressure can damage plumbing and fittings. Treat any number from a forum or video as unverified.
Air does not finish the job. Even in its compressed-air guide, Keystone says to pour about one quart of RV antifreeze into each drain, P-trap and toilet afterward, and to leave a little in the toilet to keep the seal.

Tankless and on-demand heaters (Truma Combi, AquaGo)

These heaters follow different rules.

Truma Combi. Truma’s winterizing page lists these steps:

Switch the unit off and let it cool.
Release pressure and open all taps.
Set the unit to bypass mode, following the manufacturer’s instructions.
Place a container of at least 2.64 gallons (10 liters) under the drain outlet.
Flip the yellow handle up, in line with the valve body, to drain. If water does not drain, check the clear tube for a blockage.
Turn the yellow handle back down to a right angle.
Truma recommends leaving the drain valve open for the winter.

Truma’s page lists both step 6 and step 7. If it is unclear which lever position to leave for storage, check your Combi manual or call Truma.

Truma also says it does not recommend high-pressure air or antifreeze solutions for the Combi, and that antifreeze should only be used with an installed bypass kit.

Truma AquaGo. In a Winnebago article about Truma heaters, the AquaGo basic must be winterized even if it will only see frost. The steps there: switch the unit off and let it cool, shut off the pump or water supply and open hot and cold faucets to relieve pressure, put the RV’s water heater in bypass, flip the yellow Easy Drain Lever to drain the mixing vessel, let the unit drain completely, and remove the inlet filter cartridge, not reinstalling it until you de-winterize. Then close the lever and the access door. This is a vehicle maker’s blog, so treat Truma’s manual for your exact model as the final word.

Other tankless brands. Keystone says to refer to the operator’s manual. We did not read other brands’ manuals.

Mistakes that cause freeze damage

Pouring antifreeze with no bypass. The heater tank fills with antifreeze. This is what the bypass is for. Stop and check your manual.
Using automotive antifreeze. Toxic, and not for potable systems (SHURflo, Keystone).
Turning the heater on while empty. Dometic warns that powering the heater without water covering the element may burn out the element and void the warranty. This matters in spring too. Do not switch on the electric side until the tank is full.
Forgetting the pump. SHURflo says a frozen system can seriously damage the plumbing and the pump, and that failures of this type void its warranty.
Antifreeze in a residential fridge ice maker line. Keystone says to drain that line, not fill it.
Using air with no pressure limit. See Option B.

If you find a split line or wet floor after a cold snap, see our guide on RV water damage signs and repair.

Spring: what changes when you de-winterize

We will cover this in its own article. Two points from the manuals now: check that the drain plug and low point drain caps are back in (Keystone and Dometic both have you reinstall them at the end of winterizing), and fill the heater tank before switching on the electric element (Dometic). Dometic also warns that if a heater sat unused for more than two weeks, hydrogen gas may form in the hot water line. It says to open the hot faucet at the kitchen sink for several minutes before using any electrical appliance connected to the hot water system. If you hear air escaping from the pipe, that is the sign.

When to stop and call a technician

Stop and call a qualified RV technician if:

You cannot find the bypass, or you do not have one and want antifreeze in the system
A tankless unit will not drain, for example the clear tube looks blocked
You see a leak, crack or wet area at the heater, pump or any line
Your manual gives no air pressure limit and you still want to blow out the lines
You smell propane. Dometic’s instruction: evacuate everyone, shut off gas at the container or source, do not touch any electrical switch or use a phone or radio in the vehicle, do not start the engine or generator, and call a gas supplier or qualified service technician. If you cannot reach one, call the fire department. Do not turn the gas on until the leak is repaired.

Check that your propane and carbon monoxide detectors work before you store or use the RV. Test them by the maker’s instructions. Freeze damage may fall outside a warranty or service contract, so read yours; see our extended warranty guide.

Other winter jobs (batteries, roof, tires, pests) are outside this article.

FAQ

Can I use regular car antifreeze?
No. SHURflo and Keystone both say not to use automotive antifreeze in a potable water system. Use antifreeze labeled non-toxic for potable water.

Do I need to drain the water heater if I use antifreeze?
Dometic says to drain the heater before winter storage or when freezing is possible. With Option A, you also bypass it so it does not fill with antifreeze.

Is compressed air enough on its own?
Not in the sources we read. Keystone’s compressed-air guide still has you pour RV antifreeze into each drain, P-trap and toilet after blowing out the lines. Follow your manual.

Do I winterize a Truma AquaGo if it only gets light frost?
The Winnebago article says yes, even in frost conditions.

Does freezing damage count under an extended warranty?
It depends on the contract. Read the exclusions, and see our extended warranty guide.

Sources

All pages read on 2026-10-20. Prices are not quoted in this article.

Truma, “Time to Winterize: Truma Combi” (October 17, 2022): truma.com
Dometic, 10-gallon gas-electric water heater manual (literature MPD 93756, revision A, 10/11/18): dometic.com (PDF)
Pentair-SHURflo, “RV Water Pump Maintenance” (reprinted on rvda.org): rvda.org
Keystone RV, “How to Winterize Your RV with Antifreeze” (undated): keystonerv.com
Keystone RV, “How to Winterize Your RV Plumbing System with Compressed Air” (undated): keystonerv.com
Winnebago, “Truma RV water heater maintenance and winterization”: winnebago.com

Not found or not read: a Suburban or Atwood winterizing document, an RVIA winterizing page, the Truma AquaGo manual itself, and an air pressure limit from any maker other than Keystone.