RV Water Heater Smells Like Rotten Eggs
The Short Answer: Rotten-egg smell only at the hot faucet on an RV is hydrogen sulfide from bacteria on a magnesium anode — or stagnant 6-gallon water after storage. Rotten-egg smell in the bay or the coach air is propane mercaptan until bottles are shut and a tech says otherwise. Do not treat a fuel leak as “the anode.” Do not chlorinate a live LP line.
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Search Intent & The Real Problem
You opened the exterior door or you took a shower after storage and it smelled like a matchbook or a swamp. People Google this and get residential anode articles, or they get “RVs always smell like LP.” Those are not the same repair. Anode odor is in the water. Fuel gas is in the air. A mouse in the burner is in the combustion chamber. Mix them up and you either ignore a leak in a small bay or you shock-chlorinate a Suburban while the regulator weeps.
Residential closet split: smells like a dead animal. Stick-built closet emergency: closet smells like gas. This page is the RV bay and the 6- or 10-gallon tank after storage, city-water hookups, and winterize.
What other guides get wrong
They jump to “replace the anode with aluminum” while the bay smells like fuel. They say a little LP odor at first light is normal and to keep clicking DSI. Repeated ignition trials dump unburned propane into a closet-sized box. They pour bleach through the T&P. Never through the relief valve — and never cap it. They also blame every sulfur shower on “city water” without checking whether the cold tap stinks too.
Step-by-Step Troubleshooting
Step 1: Split air vs water vs combustion. Right now.
| What you notice | What it is | Action |
|---|---|---|
| Rotten eggs in the bay, coach, or around the regulator | Mercaptan / LP leak | Leave, bottles off, do not spark |
| Rotten eggs only at hot taps; cold water fine; bay air clean | Anode + sulfate-reducing bacteria, or stagnant tank | Water-side repair below |
| Smell at the burner door, soot, nest, or a cracked sight glass | Critter or rollout in combustion | LP off. Do not fire it |
| Pink or green chemical smell, not sulfur | Winterize antifreeze still in the tank | Flush the heater, not an anode |
| Sewer smell at the dump or a dry trap, cold and hot | Black tank / plumbing, not the heater | Different system |
| Electric-only coach, bay still smells like gas | Furnace, stove, bottles, or a line — not the 120-volt element | Leave. Utility / LP tech |
- What to look for: Whether cold water stinks too (campground well / city, not the heater). Whether the odor tracks a DSI click. Badge: Suburban steel with a separate anode vs Atwood/Dometic aluminum (often a combination drain-anode, less “classic” magnesium sulfur).
- Required tools: Your nose from outside the door. No wrenches on the LP train.
Step 2: Air is propane until proven. You are done if it is.
- What to look for: Odor at the bottles, pigtail, regulator, furnace, range, or the heater solenoid. Hiss. A stove that will not light because the regulator is dumping. DSI that clicked three times into a smell — that bay has unburned LP in it.
- Required tools: Phone outside. Bottle valves. LP emergency number or a licensed RV tech.
Do not “air it out” with the interior gas switch still on. Do not soap a live leak in a rig you are sleeping in. Manifold on these boxes is typically ~10–11 in. w.c. LP — confirm the rating plate. That measurement is licensed. Gas-dead diagnosis on a clean bay: Suburban not working on gas, Atwood troubleshooting.
Step 3: Hot-water-only sulfur — anode, bacteria, storage
- What to look for: Smell at the shower, not the bay. Worse after a month in storage (six gallons of warm sulfate water is a bacteria farm). Campground well water. Suburban magnesium anode still in the tank (factory default on the steel tanks). Smell that showed up after you switched from aluminum/zinc back to magnesium.
- Required tools: After LP and 120 V are off and the tank is isolated: correct anode wrench, new aluminum/zinc or a listed RV anode, not a 50-gallon house rod stuffed into a 6-gallon boss. Do not crack the anode on a tank that still has electric on.
Repair is a new anode plus a shock of the tank if bacteria are established. Flush through the drain plug, not the T&P. Fill, heat (electric is fine if the tank is full), drain, repeat until the sulfur is gone. Bypass must be in the heat path or you are chlorinating the lines and leaving the tank filthy. Same fill rule as turned on without water.
Atwood/Dometic aluminum tanks do not grow the same anode sulfur. If an aluminum tank’s hot water stinks, look at storage, a fouled drain-anode, or campground water before you buy a magnesium rod that does not belong.
Step 4: Winterize leftover, city water, and the dump-valve red herring
- What to look for: Pink RV antifreeze in the hot stream — sweet, not rotten eggs. Bypass left in winterize so you are showering through the water heater’s leftover. Cold and hot stink: the pedestal or the fresh tank, not the heater. Black-tank odor at a shower because a trap is dry — that is not the Suburban.
- Required tools: Flush until the antifreeze color is gone. Taste nothing; look at color and smell.
A city-water regulator does not cause sulfur. It can cause a T&P drip if it has failed and the hose is at 80+ psi. That is water on the ground, not a smell.
Step 5: When the “smell” is a dying tank or a nest
- What to look for: Wet insulation going sour, rust at the jacket, water under the exterior door — treat it as a leak: leaking outside. A rodent on the burner or packed in the grate: LP off, do not spark. Soot and a rotten smell at light-off can be incomplete combustion, not an anode. Do not keep resetting DSI into that.
- Required tools: Flashlight, bottles off. If the jacket is wet, stop swapping anodes.
A 12-year Suburban that stinks and weeps is a replacement. Parts on a rotten shell are a delay.
When DIY Ends: Calling a Licensed Pro
It ended at the first whiff in the bay air. You may leave, shut bottles from outside, and later hire anode replacement on a tank that only stinks at the tap. You may not soap-test a live LP leak, dump bleach into a T&P, or fire a heater with a nest on the burner. A mobile RV tech changes anodes, chlorinates a 6-gallon the right way, leak-tests the LP train, and replaces a vessel that is rotting. A licensed LP tech handles odor in the air. Do not sleep in a coach that smells like fuel.
Frequently Asked Questions
Q: Why does my RV water heater smell like rotten eggs? A: Either propane mercaptan in the bay (fuel leak — leave), hydrogen sulfide in the hot water (anode and bacteria, worse after storage), leftover antifreeze, or a critter in the burner. Split air vs water before you buy an anode.
Q: How do I get the rotten-egg smell out of RV hot water? A: With the bay air clean: replace a spent magnesium anode (aluminum/zinc on steel Suburbans) and shock-flush the tank through the drain plug. If the air stinks, that is not an anode job.
Q: Can an RV water heater gas leak smell like sulfur at the faucet? A: No. Fuel odor is in the air. Faucet-only sulfur is the water. If both stink, leave first and deal with LP. Do not light it to “see if the shower still smells.”