Sandra Park
My water heater stopped working outside Moab in late October, and I’ll be honest: I panicked a little. Not because cold showers are the end of the world, but because I’d been on the road for three years at that point and genuinely had no idea what I was looking at when I opened that exterior access panel. Eight years later, I could diagnose most RV water heater problems in my sleep. The gap between then and now is just experience and a willingness to actually understand the system instead of immediately calling a mobile tech.
Most people assume water heater issues are complicated. They’re usually not. The majority of failures I’ve seen (and had) come down to four or five causes, and most of them you can fix yourself for under $30.
Understanding What You’re Actually Working With
| Component | Typical Cost | Time to Replace | Frequency |
|---|---|---|---|
| Anode Rod (Suburban) | ~$8 | 10 minutes | Annually |
| Electrode/Igniter | $15-25 | 15-20 minutes | As needed |
| Sail Switch | ~$20 | 20-30 minutes | As needed |
| Heating Element | $20-40 | 30-45 minutes | Every 3-5 years |
| Thermostat/High-Limit Switch | $15-30 | 15-25 minutes | As needed |
Before you start poking around, you need to know which heater you have. There are two main brands that cover probably 90% of the RV market: Atwood (now Dometic) and Suburban. They work differently enough that advice for one doesn’t always apply to the other.
Atwood/Dometic units have an aluminum tank. Suburban units have a steel tank with a glass lining, and they use an anode rod that needs annual replacement. If you’ve got a Suburban and you’ve never replaced the anode rod, do that first before anything else. A corroded or depleted rod is behind a lot of the funky smell and heating complaints people chase for weeks. A replacement rod costs about $8 at any Camping World or on Amazon, and swapping it takes ten minutes with a 1-1/16" socket.
Both types typically run on propane, electricity (120V element), or both (called DSI for direct spark ignition on the gas side). Knowing which mode you’re trying to use when something fails matters a lot for diagnosis.
When It Won’t Light on Propane
This is the most common call I get from other fulltimers. The heater clicks, tries to ignite, then locks out. Or it doesn’t even try.
First thing: check your propane supply. I know that sounds insulting, but I have personally done this. Ran out of propane and spent 20 minutes staring at the water heater before checking the tank gauge. Just verify. Then go turn on a propane burner on your stove and make sure you’ve got decent flow.
If you have gas but no ignition, here’s the sequence I follow:
Check the electrode and igniter. Open the exterior access panel and look at the burner assembly. The electrode tip should be about 1/8" to 3/16" away from the burner. If it’s cracked, coated in carbon, or positioned wrong, it won’t spark reliably. You can clean light carbon buildup with fine steel wool and reset the gap. Replacement electrodes run around $15-25 depending on the model.
Look at the burner tube itself. Spiders. I cannot stress this enough. Mud dauber wasps love to build nests inside propane burner tubes, and a partially blocked tube causes erratic ignition or no ignition at all. I use a piece of small-diameter wire or a pipe cleaner to clear the tube, then blow compressed air through it. This has solved the problem for me personally at least twice.
Check the sail switch. This is a small flap inside the combustion chamber that confirms airflow before allowing ignition. If it’s stuck, bent, or has debris on it, the heater won’t light as a safety measure. You can see it when you look into the burner area. It should move freely. On older Suburbans especially, this switch fails or gets stuck with corrosion. Replacement is straightforward, and the part is usually under $20.
If none of that works, you’re looking at either the ECO (energy cutoff) switch, the circuit board, or a gas valve issue. The ECO is a thermal fuse that trips if the water gets dangerously hot. It’s a small button or reset on the unit, sometimes accessible from inside the RV, sometimes from the exterior panel. Push it. Seriously, check that before anything else electronic.
The Electric Element Side
If you’ve got a combination unit and propane works fine but the electric mode doesn’t heat water, that’s almost always the heating element or the thermostat.
The element is submerged in the tank and screws in just like a residential water heater element. They fail. It’s not dramatic, it just happens after a few years. You can test continuity with a basic multimeter. A failed element reads open (infinite resistance) instead of the expected low resistance (around 10-16 ohms for most RV elements). A replacement element for most units runs $20-40. The Atwood/Dometic 91602 is a common one I’ve replaced personally.
Before you pull the element, though: turn off the water heater, relieve pressure at the pressure relief valve, open a hot water faucet inside to break the vacuum, then drain the tank from the exterior drain plug. Don’t skip draining it. I’ve seen people try to swap elements with water in the tank and it’s exactly as messy as you’d expect.
The thermostat (sometimes called the high-limit switch on the electric circuit) is another failure point. If it’s tripped or failed, the element gets no power. On most units it’s clipped directly to the tank near the element and held by a bracket. Test it for continuity with your multimeter. If it’s reading open, you’ve found your problem.
One thing I’ll be honest about: if you’re not comfortable with multimeter work or working around 120V, there’s no shame in calling a tech for the electric side. Propane stuff is very accessible. Line voltage, if you’re not familiar with it, deserves respect.
Why Your Hot Water Smells Like Rotten Eggs
This surprised me when I first learned it. So many people I’ve met are living with sulfur smell in their hot water for months, assuming it’s the water supply. It usually isn’t. It’s the anode rod reacting with bacteria in the tank.
This happens most often in Suburban units after the rig sits unused for a while, especially if you’re using well water or water with higher sulfur content. The fix is replacing the anode rod (see above) and then shocking the tank with a diluted bleach solution. I use about 1/4 cup of household bleach mixed into a gallon of water, pour it into the tank through the anode rod port, fill the rest of the way, let it sit for several hours, then fully drain and flush.
If you’ve got an Atwood/Dometic (aluminum tank, no anode rod), sulfur smell can still happen from bacterial growth. Same process, minus the rod replacement.
The Pressure Relief Valve Is Dripping
This one freaks people out more than it should, and it also gets ignored more than it should. Both are mistakes.
If your T&P (temperature and pressure) relief valve is dripping steadily, there are two possibilities. Either the valve itself has failed and needs replacement (they’re $15-25 and should be replaced every few years anyway), or your water pressure is too high and the valve is doing exactly what it’s supposed to do. If you’re hooked up to city water without a pressure regulator, you could easily be seeing 80-100 PSI coming in, and that’ll cause the T&P to weep.
Get a water pressure regulator if you don’t already have one. I run a Watts 263A adjustable regulator set to about 55 PSI. Non-negotiable piece of gear in my opinion. Saves your water heater, your fittings, your hoses, all of it. (Note: that’s an affiliate link and this site may earn a commission on purchases.)
If pressure is fine and the valve still drips, replace the valve. Don’t try to clean or reset a dripping T&P valve. They’re not designed to reseat reliably once they’ve opened, and a failed T&P valve is a safety issue, not a minor inconvenience.
What Most Troubleshooting Guides Won’t Tell You
Sources
The bypass valve. When you winterize an RV, you (or someone) engages the water heater bypass to keep antifreeze out of the tank. If spring rolls around and you forget to switch it back, you’ll get hot water at some fixtures but not others, or dramatically reduced flow, or the heater will cycle constantly trying to heat water that isn’t really in the tank properly. I’ve seen this trip up experienced RVers. It’s embarrassing but extremely common. Check your bypass valve configuration before you diagnose anything else in spring.
Also: if your water heater is taking forever to produce hot water or you’re constantly running out, the problem might not be the heater at all. Check for a cross-connection between your hot and cold lines. This happens sometimes after plumbing work or fitting failures, and cold water bleeds back into the hot side. A quick test is simple. Turn off cold water supply and open a hot tap. If water keeps flowing, you’ve got a cross-connection somewhere.
Eight years in, I still carry a spare anode rod, a spare electrode, and a small jar of pipe cleaning brushes. Costs me maybe $40 in parts and they’ve saved me from cold showers more times than I can count. The water heater is one of those systems that’s really not that intimidating once you understand what each piece does. Open the panel, take a look, and trust yourself to figure it out.
Photo: Juan Hernandez Jr via Pexels
