How To Winterize An RV Tankless Water Heater

Learning how to winterize your RV tankless water heater is important for preparing your RV for the harsh winter weather if you want to avoid repairs and damage. The tankless water heater is one component that needs proper winterization at the start of winter or when heading to locations that are prone to freezing temperatures. So how can you effectively winterize your RV tankless water heater? 

To winterize your RV tankless water heater: 

  • Unplug or turn off the power to your tankless water heater.
  • Shut off and disconnect the water supply to the inlet of the unit. 
  • Disconnect the outlet and let the water drain into a bucket or dish below.
  • Use compressed air to blow any remaining water out the internal pipes. 

Protecting the tankless water heater in your motorhome or trailer from freezing temperatures is a simple procedure. However, there are a few important details you don’t want to miss or it can lead to damage and costly repairs. 

Winterizing a Tankless Water Heater

The process of winterizing your RV should always include the tankless water heater which is usually the same for both propane instant hot water heaters and electric hot water heaters. 

Many manufacturers do not recommend using antifreeze inside the water heater because it can cause damage to the internal components and will void the warranty. If you are using a non toxic antifreeze like Propylene Glycol in the rest of your RV water system install a bypass around the hot water heater to avoid getting antifreeze inside the unit.  

If your tankless water heater’s owners manual allows for the use of antifreeze in the unit you won’t have to worry about the bypass. However, it’s important to disconnect the power from the unit because heating the antifreeze can cause damage to the internal components of the water heater.

Many modern tankless water heaters have an internal antifreeze device which heats up to protect the unit from freezing during cold periods. This is not a long term storage solution as it requires power and a failure can be catastrophic to your motorhome or 5th wheel’s water heater. 

Check out our Complete Guide to Tankless Hot Water Heaters for more information

How To Winterize Your Tankless Hot Water Heater With Compressed Air

Draining the instant hot water heater and blowing it out with compressed air is the best way to protect your unit from damages during winter storage.

Below are steps you can take to winterize your RV using the compressed air method.

Turn Off the Gas Supply and Electrical Power

As a rule of thumb, power sources should always be turned off before beginning the winterizing process. Use the main valve on your gas supply line to turn off the propane. If you’re using an electric-powered tankless heater, either turn off the power at the circuit breaker panel or unplug the power cord. 

Shut Off Water Supply and Allow the Water To Cool

If your rig is connected to city water shut it off at the supply and disconnect the hose from your RV. If your hot water heater was recently in use, wait 30 minutes to an hour to allow the water to cool before draining it.

Open Taps and Release the Pressure From Your RV’s Plumbing System

Drain your water system from the lowest point in the plumbing lines, open all the taps to allow air into the lines to allow them to drain properly.

Be sure to wait until all the water drains before disconnecting the water pipes from your tankless water heater. 

Disconnect the Water Pipes

After the system has drained, place a bucket under the unit to collect the remaining water that was trapped inside. 

Disconnect both inlet and outlet water connections from your tankless water heater. If you find yourself struggling with this, consult your owner’s manual for assembly and disassembly tips.) Once you have the pipes disconnected, Wait for the water to drain completely before moving to the next step.

Turn On the Compressor

Adjust the air compressor to the 30-40 psi range and connect it to the inlet connection of the water heater. Once you’re done connecting the air compressor to the water heater, you’re ready to turn it on.

For the best results, regulate the compressed air in smaller bursts, taking short breaks before each pump. Pushing the compressed air all at once might exert excess pressure and you risk damaging the internal water lines. 

Pump the compressed air until water no longer drips out the bottom connection of the unit. Now you can consider your RV water heater to be safely winterized. 

How To Winterize Your Tankless Hot Water Heater With RV Antifreeze

The antifreeze method is a great way to winterize your RV’s system and keep your tankless hot water heater safe during its idle months. However, before filling your system with an antifreeze (non-toxic), it’s important to observe the recommendations provided by your RV’s manufacturer. Also, check on the ingredients of your preferred antifreeze to ensure it doesn’t corrode your RV’s plumbing system 

Disconnect Your RV From the External Water Source

If your RV is connected to an outside water source, shut off the water supply and disconnect it. You’ll be draining the water system to prevent the antifreeze from getting diluted and becoming ineffective.  

Turn Off Electrical Power and Gas Supply

To turn off the electricity, you’ll need to unplug the power supply or use the circuit breaker panel to turn the power off. You’ll know that your unit is completely shut down when the display (on the front of the unit) turns black without any LED notifications.  

Allow Hot Water To Cool

If you haven’t used your tankless water heater in a while the water should be cold. But if you have used it recently, you may need to give the unit some time to cool down before draining the water. 

Open All Faucets

It’s impossible to successfully winterize your tankless water heater without letting all the water out. Therefore, you should open all faucets to allow the system to drain and release pressure from your RV’s plumbing system. Ensure that all taps are opened to speed up the process and ensure that water inside the system is effectively drained. 

Attach an Intake Siphon to the RV Antifreeze

If you are using an external hand pump, you’ll need to attach the hand pump’s intake siphon to the antifreeze bottle. Next, connect the pump’s output hose to the city water inlet, close all the faucets, and drain valves that you’d opened earlier. 

Start Pumping the Antifreeze

Using the external hand pump, you’ll need to carefully pump all the antifreeze into your RV’s plumbing system. To target the tankless water heater, open the hot water taps and shower until a pink-colored liquid runs out the taps and showers. 

Once you spot the antifreeze running out of your hot water faucets, you’ll know that your water heater is well winterized and ready for the harsh winter weather. 

Final Thoughts

As we’ve observed throughout the article, winterizing an RV tankless water heater isn’t such a tall order. The trick, however, is to winterize before you head out to a location notorious for freezing temperatures or before winter starts. 

To ensure you successfully winterize your RV’s tankless water heater, you should always start by draining your RVs plumbing system. Remember to regulate the air compressor’s pressure to avoid damaging your system’s lines.


Beau is an electrical engineer with a knack for DIY repair and construction. When he's not tinkering with his projects he's on the road travelling and enjoying an exciting lifestyle with his young family.

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