RV water heater not working: no hot water on gas or electric

Know your water heater

Most RV tank water heaters hold a small amount of water and can run on propane, 120V electric, or both. Some RVs have tankless (on-demand) propane units instead. The diagnosis for those is similar on the gas side, but follow the manufacturer's manual.

Two common tank designs matter for maintenance:

• Steel tank: uses a sacrificial anode rod that screws into the drain hole.
• Aluminum tank: has a built-in anode layer and uses a plain drain plug. Don't fit an anode rod unless the manufacturer specifies it.

Danger: The water heater runs at high temperatures and pressures. Before removing the drain plug or anode, turn off gas and electric modes, let it cool completely, turn off the pump, disconnect city water, and open a hot tap and the pressure-relief valve to release pressure. Never run the electric element with the tank empty. It will burn out almost instantly. If you smell propane, stop and see RV propane problems: smells, weak flames, regulator issues and leak testing.

Step 1: Check the bypass valves first

After winterizing, the water heater bypass valves are set to send water around the tank. If they're still in bypass, the heater can't heat anything, and you'll be running the electric element with no water. Check that:

• The bypass valve(s) are in normal (not bypass) position.
• The tank has been filled. Open a hot tap until water flows steadily with no sputtering, which means the tank is full.

Electric mode: no hot water

1. Is the switch on? The electric element switch is often hidden. It could be on the monitor panel, in a cabinet, near the floor or on the heater itself.
2. Check the breaker for the water heater in the 120V panel.
3. Reset the high-limit (ECO). Many units have a reset button on the thermostat assembly behind the outside access door, usually under a cover. Overheating or a dry-fire trips it.
4. Test the element. With all power off and the wires disconnected, measure the element's resistance with a Digital multimeter (auto-ranging, with DC amps). A reading of infinite/open means it has burned out. Compare with the expected value for its wattage (resistance = volts² ÷ watts, so a 1,440 W element at 120 V is about 10 ohms). Elements usually fail from dry firing or scale buildup.
5. Replacing the element: drain the tank, unscrew the old element with the correct socket, fit the new element of the same wattage and voltage with a new gasket, then refill the tank completely before restoring power.

Gas mode: no hot water

Direct spark ignition (DSI) models

You flip a switch inside, and the heater tries to light. A "check" or fault light means it tried and failed.

1. Propane supply: Do the stove burners light normally? If not, fix the supply first.
2. Air in the lines: After a tank change or storage, it may take several tries. Light the stove to purge the line, then reset the water heater by switching it off and on.
3. 12V power: DSI boards need good 12V. Check the fuse and battery voltage.
4. Listen and look: Open the outside door (with the cover off) and watch while someone switches it on. You should hear the gas valve click and see sparking at the burner. Sparking with no flame suggests gas supply or a blocked burner tube. No sparking points to the board, igniter or wiring.
5. Insects and webs: Spiders love the burner tube. A blocked tube causes poor ignition, a yellow flame, or soot. Cleaning the tube is common maintenance, but if you're not sure how, have it done.

Pilot-light models

Older heaters have a manual pilot with a thermocouple. If the pilot won't stay lit after you release the knob, the thermocouple may be faulty or not positioned in the flame. Wind blowing into the access door can also blow out pilots.

Water is lukewarm or runs out fast

• Mixing valve or bypass leak: A partly open bypass valve mixes cold water with hot.
• Sediment buildup: Scale and sediment insulate the bottom of the tank and the element. Flush the tank with a tank rinser wand.
• Electric-only: Element alone heats slowly. Run gas and electric together for faster recovery, if your model allows it.
• Thermostat: Faulty thermostats can shut off early.

Relief valve dripping

A drip from the pressure-and-temperature (P&T) relief valve during heating is common in RV water heaters. As water heats it expands, and if the small air pocket at the top of the tank has disappeared, the valve releases the excess. To restore the air pocket: turn off the heater and water supply, open a hot tap, and briefly lift the relief valve lever until water stops flowing. Then close everything and refill. If the valve drips constantly or gushes, the valve may be faulty and should be replaced, or the pressure in the system may be too high. Use a water pressure regulator at campgrounds.

Annual maintenance

1. Drain and flush the tank at least once a year. Many owners do it at winterizing time.
2. Check the anode (steel tanks). Replace it when much of the metal has been eaten away. Use a 1-1/16" socket for most models. Use thread tape on the anode threads as the manufacturer recommends.
3. Clean the burner area and check the exhaust vent for nests.
4. Check the outside door seal and screens.

Winterizing

Drain the tank, leave the drain plug out or the anode removed over winter (store it inside so you remember), and set the bypass so antifreeze doesn't fill the tank. Details in How to winterize an RV for a Canadian winter (step by step).

When to call a pro

Get a certified technician for gas valve or control board replacement, any propane leak, a leaking tank (the tank itself, not a fitting), soot or scorch marks around the heater, or if your tankless unit throws error codes you can't clear.