Having hot water is an amenity that most campers hold as an essential. A water heater is a standard component that comes with most RVs. Dometic is a very common brand of water heater and here we will help you understand the operation, maintenance, and technical tips you may need to keep the hot water flowing.  There are 2 different options when it comes to water heaters, those with a tank and tankless ones, this article will cover the style with an actual tank.  

A gas leak check is recommended yearly for the RV gas system before operating the appliances.  You should also ensure all of your safety devices are up to date and operational. Below we will take you through the operation, maintenance and some diagnostic tips on a Dometic Water Heater.

Dometic RV Water Heater Operation and Maintenance


Pop-off Valve or Pressure Relief Valve

  • Pop off valves are set to a 250-degree or 150psi pressure mark.  This means if the tank were to hit or exceed these marks it will open up and relieve the pressure on the tank.
  • This is a safety component to keep the tank from cracking open from over pressure.  Warning the water that exits the valve will be hot.
  • It is normal for this valve to drip water when the water heater is being operated.  Due to expansion the water may reach a certain level and drip out of the valve.        
  1. To remedy this shut the system off and allow water to cool.
  2. Shut off the city water source or water pump. 
  3. Once the water has cooled, crack open the pop-off valve and allow water to exit the tank. Or turn on the hot valve fixture at a sink.
  4. This will allow an air pocket into the top of the tank.  Over time this air pocket will become smaller due to the expansion of the water.  So, it is common to have to do this after extended usage.

Gas Valve

  • The gas valve will operate automatically when the gas switch is initiated.   From that point the valve opens emitting gas into the mixture tube and the igniter will fire off and light the fuel to heat the water in the tank.

ECO and Thermostat

  • The ECO is a closed switch that sends voltage to the solenoid valve to initiate the water heater.  The switch opens if the water temperature exceeds 180-degrees, protecting the water heater from damage.
  • You will also have a Thermal cutoff fuse.  This is an inexpensive safety device designed to cut power to the water heater should the temperature around the heater and burner rise to unsafe levels.

Control Board

  • The control board receives the signal from the electric or gas switch and initiates the process of heating the water.  It also controls when the water heater will shutoff and turn back on to keep the water at the appropriate temperature.

110 Volt Heating Element

  • The 110 Volt heating activates when electric is chosen as the heat source.  It will initiate and heat the water to the appropriate temperature. 


  • The exhaust will emit the burn off from the gas operation. This grill will be hot during operation and contact with it should be avoided.

Drain Plug

  • The drain plug when removed will drain the water out of the tank of the water heater.




  • When the Electric switch is operated inside the unit, the heating element will activate and heat the water.
  • It will turn off on and as needed and stay active as long as the switch is on.



  • When the Gas switch is operated inside the unit, the gas valve will open and the igniter will begin to tick, eventually igniting the flame.  This will then begin to heat the water.
  • It will turn off on and as needed and stay active as long as the switch is on.

Operation Tips

  • Both Gas and Electric can be used at the same time to heat the water faster.  This is useful when taking back-to-back showers.
  • If you have a 30 Amp service on your RV it is a good idea to use the gas function over electric to save amperage usage for other appliances on your unit.  If you are trying to heat water on electric as well as run a microwave and Air Conditioner it will trip the main breaker.




  • If your water heater is not functioning on electric, you should first check the breakers on the inside of your RV to ensure no breakers are tripped.  Next, you should check the power poll your RV is plugged into.
  • Your water heater also needs 12 volts to operate on either function.  Checking the 12-volt fuse for the water heater to ensure it is not blown is also something to check as well as making sure your charging system is operational and your battery is good.


  • If your water heater is not functioning on gas, you should first ensure that your Propane tanks are at a sufficient level.
  • Your gas operation must have 12 volts to operate.   Checking the 12-volt fuse for the water heater to ensure it is not blown is also something to check as well as making sure your charging system is operational and your battery is good.
  • DSI light on the control panel inside the RV is illuminated.
  • This means that the gas option has a fault and has not lit.
  • Most commonly this will result from initiating the gas switch, hearing the igniter trying to light (the ticking noise from the water heater), but the end result is nothing and the DSI light comes on.
  • If this happens, you should go to your stove top and turn on and light one of the burners.  Allowing the air to bleed out of the gas system.  You should have a crisp blue flame.  In the event, you have a poppy orange flame or still no ignition, continue to bleed the air out while trying to ignite and allow it to burn until a crisp blue flame is reached.
  • Once this is completed then turn off and turn back on the gas switch for the water heater to see if it will initiate.
  • Air in the system after it has been shut off or tanks have been changed is the #1 issue when there is a fault in the gas function of the water heater.



  • The burner tube should be cleaned out using a blower tip from an air compressor. It is common for insects to build nests blocking the burn off exhaust from exiting the tube.
  • This can cause inefficiencies in the system as well of backup of gas causing the system to fault.  If you notice a black smoking carbon exhaust emission you should shut the system off and be sure the exhaust tube is not blocked by any foreign debris.
  • The tank should be drained and flushed once a year to prevent calcification buildup in the reservoir.  Be sure to refill the tank before the next use.
  • Check for sealant around the cover to ensure there is no cracking or pealing around it allowing water entry.
  • Check the sealant round the gas line under the cover as well as the hinges to ensure there is no cracking or peeling in that area as well.


For a better understanding on Dometic RV Water Heater Operation and Maintenance, check out this video: 

This content is not a legal standard or regulation, and does not create any new legal obligation.  It is advisory in nature, informational in content, and is intended to assist and educate consumers in the use and enjoyment of their recreational vehicles.  Great American RV Superstores does not hereby make any warranty, express or implied, and does not assume any liability with respect to the use of, or damages resulting from the use of any information, method or process included in this content.