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How To Winterize Your RV Tankless Water Heater

Cold weather doesn’t have to stop you from RVing, but you must prepare your rig to handle all the elements that winter brings when not using it. If not, you could do severe and expensive damage to it. However, many manufacturers are installing tankless water heaters on their newest models. Do you need to winterize a tankless water heater?

Today, we’ll answer this crucial question and give you some helpful tips. Keep reading if you want to prepare your RV’s tankless water heater for winter. Let’s get started!

How To Winterize an RV Tankless Water Heater

You need to winterize your rig if you own an RV and live in a location that experiences freezing temperatures, especially if you have a tankless water heater. This protects the plumbing system, including the water heater, from potential damage. Unfortunately, the winterization process varies depending on the RV. It’s best to check the owner’s manual for your RV or contact the manufacturer for the specifics. Here are the general steps for winterization however.

1. Determine Your Tankless Water Heater Make/Model

You must know its make and model to winterize and protect your tankless RV water heater from freezing temperatures. Locate and read through the winterization instructions for your model to familiarize yourself with the specifics of your unit. Each model may have slightly different instructions.

2. Bypass and Drain the Water Heater Completely

The next step is to turn off the water in your RV and to the water heater and drain the water heater entirely.

Water heaters are not winterized the same way as the rest of the water lines and should have bypass valves installed behind them. These valves can be turned to prevent water from flowing to the heater and bypassing it completely.

Once bypassed, the water heater needs to be drained of all water. Most water heaters have a drain to make it manageable to drain the water. This can be messy, and you may get wet, so be careful.

3. Winterize Your RV Water Lines

One of the most crucial tasks when winterizing your RV is to remove water from the plumbing lines. You can use an air compressor or RV-safe antifreeze to accomplish this task. However, if you use an air compressor, use a pressure regulator to avoid damaging your water lines.

Many modern RVs come with features that make the winterization process incredibly convenient. However, these winterizing settings should bypass the water heater because most RVs have water heaters that store several gallons of water in a tank. You’ll use a tremendous amount of antifreeze if you do not bypass the water heater in these situations.

Pro Tip: Make winterizing your RV easy with this guide on How to Use RV Antifreeze to Winterize Your Rig.

Installing Rv anti-freeze to winterize RV
Using RV anti-freeze is a key tool while winterizing your rig.

4. Turn Off the Power and LPG to the Water Heater

When you winterize your RV tankless water heater, turn off all power and propane. You don’t want it to turn on, whether sitting empty or filled with antifreeze. There’s also a chance that a propane leak could develop during the winter. However, shutting off your propane can help avoid this scenario and ensure you don’t waste any propane.

5. Remove the Water Filter

A crucial step not to forget is to remove the water filter. This step occurs when draining the water from the water heater lines before blowing out the system. You must remove the water heater drain and filter to allow the air to push out any water inside the water heater. Stay clear of these holes; water will fly out as you send air through the lines.

Don’t let the snow stop you from RVing during the winter.

At What Temperature Does an RV Tankless Water Heater Freeze?

If your RV is not being used or heated, then your heater will begin to freeze at 32F or 0C. It will, however, not instantly freeze solid as the further and longer the temperature is below 32 degrees Fahrenheit (0 degrees Celsius), the more likely the water heater will freeze. So if the temp dips overnight briefly and comes back up, it may not freeze solid.

If, however, you are using and heating the RV, the water heater should be good to much colder temperatures. Most on-demand water heaters have freeze protection built in, and as long as they are kept on, they can operate well below freezing.

Truck camper in snowy campsite
When temperatures drop, you will need to winterize your rig. We had an on-demand water heater on this rig.

What Happens When a Tankless Water Heater Freezes?

Freezing temperatures can severely damage an RV, including a tankless water heater. However, nothing will happen if you prepare for the cold weather by draining and winterizing your unit. It will be safe from the potential damages that owners experience from freezing temperatures.

When a tankless water heater freezes, the water inside the unit expands as it turns to ice. This expansion can damage the unit, causing cracking or bursting of the heat exchanger, which is the component that heats the water. If the heat exchanger cracks or bursts, water can leak into the unit’s electrical components, potentially causing a short circuit and other electrical problems.

Additionally when water pressure is applied leaks and other plumbing issues will occur. If you don’t properly drain the unit before it freezes, the ice can also damage the water pump and other parts of the plumbing system.

A unit impaired from freezing water may not work correctly and will likely require servicing. In many instances, the damage may be so severe that the water heater is beyond repair.  If that’s the case, you’ll need to replace it.

Pro Tip: Want to install a new tankless water heater? We found the 6 Best RV Tankless Water Heaters for Instant Hot Water.

Can You Use Your RV Tankless Water Heater in Freezing Temperatures?

It is possible to use your RV tankless water heater in freezing temperatures. However, it must remain on, or you could put it in a risky situation. Many tankless water heaters come with cold weather settings or sensors, so they stay on and keep themselves warm to avoid damage. 

Note that in cold weather the water entering the unit will be so much colder that the tankless heater may be slower to operate or have a harder time maintaining water temperature.

However, these features require you to maintain a supply of propane. If not, the water will not stay hot, and the unit will freeze. If you plan to leave your RV for an extended time during winter, it’s best to winterize it. It’s better to be safe than sorry.

tankless water heater
Winterize your RV tankless water heater to ensure you can always have a warm shower no matter the weather.

Can You Put Antifreeze in a Tankless Water Heater?

Unfortunately, there’s no clear-cut answer to whether you can put antifreeze in a tankless RV water heater when you winterize it. Some manufacturers, like Truma AquaGo, specifically state not to put antifreeze in the unit. However, not all manufacturers take a stance.

In general, we don’t recommend filling the lines with antifreeze. These lines can get incredibly hot and burn the sugar in the antifreeze if the water turns on or you don’t remove it from the system altogether. Its always best to drain your water heater instead of adding antifreeze.

Do Tankless Water Heaters Need to Be Flushed Every Year?

Just because you have a tankless water heater doesn’t mean there won’t be some annual maintenance. Flushing a tankless water heater is typically a part of its yearly maintenance. This helps remove any buildup of minerals and sediment that can accumulate and reduce the unit’s efficiency. Regular flushing also helps prevent corrosion and extends the water heater’s lifespan. Some units like the Truma aquago have a sensor that counts the amount of water it heats and will alert you to when it needs to be flushed.

If you need help with how to flush your tankless water heater correctly, it is best to consult the manufacturer’s instructions. Regular maintenance and flushing can ensure that your tankless water heater operates efficiently and effectively.

Pro Tip: If spring has sprung, use this guide on How to De-Winterize Your RV: Get Ready for Camping Season!

How to Clean and Decalcify the Truma AquaGo On-Demand RV Water Heater

Winterize Your Tankless Water Heater to Prevent a Catastrophe

There are few things worse than preparing for an adventure and discovering a catastrophe in your RV. Depending on the situation, this could derail your plans and make it nearly impossible to enjoy your camper. Winterizing your entire RV, including the tankless water heater, is a task that requires you to take your time. One mistake during this process could be costly. Take your time and do it correctly to prevent a catastrophe!

What are your tips for winterizing your RV? Tell us in the comments!

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About Tom and Caitlin Morton

Tom & Caitlin Morton of Mortons on the Move gave up the stationary life for one where they are constantly on the move. They are full-time travelers, television hosts, and digital media producers.
They left their jobs, sold their house and possessions, and hit the road in September 2015 in their full-time “home on wheels”. Since then they have traveled the US, Canada, and even internationally by RV.
Now, they are Discovery Channel & PBS TV Co-stars of “Go North” on Amazon Prime Video, co-founders and instructors of RV Masterclass, and contributing authors for and an Arizona travel guide.

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