How an RV Water Heater Works

The kinds you will find

Most RVs have a tank water heater that holds six or ten gallons. It heats on propane, on 120 volt power, or on both at once. Newer rigs may have a tankless unit that heats water only as it flows.

Suburban tanks are steel with a glass lining. They need an anode rod to stop rust. Atwood tanks, now sold by Dometic, are aluminum and do not use an anode. Look at the plate on the outside door to see which you have.

Fill it before you turn it on

Never turn on the electric switch with an empty tank. The heating element burns out in a minute with no water around it. This is the most common water heater repair we see.

1. Make sure the bypass valves are set for normal use, not winter.
2. Turn on city water or the pump.
3. Open a hot tap inside and let it run until only water comes out, with no spurts of air.
4. Now turn on the gas switch, the electric switch, or both.

When there is no hot water

1. Check that the switch inside is on. Some rigs have a second switch outside by the tank.
2. On gas, listen for a click and a whoosh at the outside door. If it tries three times and stops, turn it off and on again. Air in a new propane line can take a few tries to clear.
3. Check that the propane tanks are open and not empty.
4. On electric, check the breaker for the water heater in the panel.
5. Check the bypass valves. If they are still in winter mode, the tank stays empty.

Draining and the anode

Drain the tank before storage and once or twice a year. Turn it off, let it cool, and open the pressure relief valve to let air in. Then pull the drain plug or the anode rod.

Look at the anode rod when it comes out. If it is eaten down to the steel core, put in a new one. Wrap the threads with plumber's tape. Never run a Suburban tank without its anode.

A little drip from the relief valve while the tank heats is normal. The water grows as it warms. A steady stream is not.

When to call a shop

Call a shop if you smell propane at the outside door, the relief valve pours water, the tank leaks from the body, or the burner flame is yellow and sooty.

The maker's own manuals

These guides cover how most RVs work. Your own rig may differ, so check the manual for your make and model.

• Suburban · Furnaces and water heaters
• Dometic · Fridges, air conditioners and awnings
• Every maker we link to