Winterize an RV Tankless Water Heater by Draining All Lines and Using Compressed Air or RV Antifreeze

To winterize an RV tankless water heater, first turn off all power and gas. Open the low point drains and the exterior drain plug to remove water. Finally, use an air compressor at low pressure to blow out the lines or pump non-toxic RV antifreeze through the system to prevent internal freezing and cracking.

Steps for Draining the System

1. Shut off the water pump and disconnect any external water sources to prevent further pressurized flow into the heater.
2. Turn off the power switch and the gas supply dedicated to the heater to ensure the unit does not ignite without water.
3. Open all hot and cold faucets throughout the vehicle to allow air to enter the system and break the internal vacuum.
4. Locate and remove the drain plug or open the exterior valve on the tankless unit to empty the heat exchanger completely.

Winterization Method Comparison

Technical Tips for Tankless Units

• Check the Inlet Filter: Many tankless units feature a small inlet water filter. Remove this component to ensure no trapped water remains behind the mesh, as this could cause the housing to crack in freezing temperatures.
• Control Air Pressure: If using compressed air, set the regulator to a maximum of 30 PSI. Higher pressure can damage the sensitive flow sensor or internal copper piping within the heater unit.
• Avoid Bypass Valves: Unlike traditional storage tanks, most tankless models should not be bypassed during the antifreeze process. The small copper tubes in the heat exchanger require the fluid to prevent expansion damage.
• Verify Fluid Flow: Run the 12V water pump until a deep pink color is visible at every hot water tap. This confirms that the water inside the heater has been fully displaced by the protective solution.