RV water heater not getting hot? Here's the fix.
Cold showers ruin trips. Walk through the exact checks for Atwood and Suburban water heaters before you call a tech.
An RV water heater that won't heat is one of the most common reasons trips end early. The good news: most water heater problems are simple, free to fix, and traceable to one of about six things. This guide walks through the exact checks for Atwood (now Dometic) and Suburban water heaters, the two brands on 95% of North American RVs.
1. Is the bypass valve set correctly?
This is the #1 reason new RVers get cold water all winter and don't know why. The water heater has a bypass valve (or three) used during winterization to keep antifreeze out of the tank. If left in bypass mode, water flows around the tank instead of through it, so it never heats.
Look behind the water heater (usually accessible from inside a basement compartment or under a bed). Find the bypass valves and turn them to the normal/summer position. Run hot water for 30 seconds, you should hear the tank fill.
2. Check the GFCI for the electric element
If your unit has electric heat (most do), there's a GFCI outlet somewhere in the rig that protects the heating element circuit. It's usually in a bathroom or galley outlet. If tripped, the electric element won't work and the unit reverts to propane only.
Press the reset button on every GFCI in the rig. A tripped GFCI you didn't notice is a 30-second free fix that catches a lot of people.
3. Test propane flow
Light another propane appliance (stove burner or furnace) to confirm propane is flowing to the rig. If the stove doesn't light either, the tank is empty, off, or the regulator is iced. Fix the propane supply first.
If propane is fine elsewhere but the water heater won't light, the burner orifice may be clogged, mud daubers love water heater burner tubes. Pull the cover and visually inspect.
4. Atwood/Dometic: check the ECO and high-limit
Atwood units have an ECO (Energy Cut Off) high-limit switch on the back of the tank. If the tank overheated once (often from being run dry), the ECO trips and won't let the burner fire. Press the small reset button in the center, you should hear a click. If it won't reset, the ECO is bad ($25 part).
5. Suburban: check the thermocouple
Suburban units use a thermocouple in the burner flame. If the burner lights for a few seconds and then shuts off, the thermocouple isn't sensing flame, it's either dirty, loose, or dead. Pull the burner assembly, clean the thermocouple tip with fine sandpaper, and reinstall. Replacement thermocouples are $15.
6. Check for an air lock
If the tank is bypassed and you switch out of bypass with the pump on, air can get trapped at the top of the tank, blocking water from reaching the element. Open every hot water tap in the rig (sink, shower, outdoor shower) and run them with the pump on for 60 seconds until water flows steady. This burps the air out.
Still stuck?
Camphost is a free AI co-pilot that walks you through RV problems one step at a time, and helps you find a mobile RV tech if simple fixes aren't working.
Open CamphostFrequently asked questions
How long does it take an RV water heater to heat up?
A 6-gallon Atwood or Suburban tank heats from cold in about 20 minutes on propane, 60-90 minutes on the 1500W electric element, or 15-20 minutes running both. A 10-gallon tank takes about 50% longer.
Can I run my RV water heater on electric and propane at the same time?
Yes, if your unit has both, running both cuts heating time roughly in half. There's no harm in it. Many full-timers do it routinely for fast morning showers.
Why does my RV hot water run out so fast?
A 6-gallon RV tank gives about 4-5 minutes of mixed shower water. To extend it: lower the bathroom flow with a low-flow showerhead, take 'navy showers' (wet, soap, rinse), or use the recirculation valve if your rig has one. Or upgrade to a tankless water heater.
Is it safe to leave my RV water heater on while driving?
On electric (when plugged into shore power, which usually means you're not driving), no concern. On propane, most RVers turn the LP off while driving and refilling fuel. Some states and tunnels require it. Modern RV water heaters have automatic relight when LP is restored.