An RV smells like sewer when black or gray tank odor gets past something: a blocked tank vent, a dry toilet bowl or worn seal, a dry sink or shower trap, or a stuck air admittance valve. If the toilet smells as you flush, check the black tank vent first; Dometic's toilet manual lists a plugged tank vent, or odor from the tank contents, as the reasons for smell while the flush valve is open. If the smell hangs around between flushes, check that about an inch of water sits in the bowl and that the flush ball seal and floor seal are intact, then run water into every sink and shower drain to refill dry traps and replace any air admittance valve that no longer closes. A rotten egg smell is a different problem, and a possible propane leak comes first. Once the source is fixed, AIRLOCK One RV clears the smell left in the air through the rooftop AC whenever the fan runs.
Where and when the smell shows up
The timing and the spot narrow it down fast. Start with the row that matches the smell.
| When or where you smell it | Likely cause | What to check or do | Source |
|---|---|---|---|
| While you flush (flush valve open) | Plugged black tank vent | Clear obstructions from the vent (see the tank owner's manual) | Dometic 300 series toilet manual |
| While you flush (flush valve open) | Odor from the tank contents | Add a black tank deodorant | Dometic 300 series toilet manual |
| Between flushes (valve closed) | No water in the bowl | Add water to the bowl; keep about 1 in. (24 mm) in it | Dometic 300 series toilet manual |
| Between flushes (valve closed) | Damaged flush ball seal | Recondition the seal, or replace it | Dometic 300 series toilet manual |
| Between flushes (valve closed) | Damaged floor flange seal | Replace the floor seal | Dometic 300 series toilet manual |
| At a sink or shower drain | Dry P-trap | Run water into the drain to refill the trap | Daisy RV |
| Stronger inside the sink cabinet | Air admittance valve not closing | Replace the valve | RV Enthusiast; Daisy RV |
| Hot water only, rotten egg smell | Sulfur water reacting in the water heater | Chlorinate the water system; replace the anode rod as needed | Suburban water heater guide |
| Rotten egg smell in the air, near appliances or anywhere inside | Possible propane leak | Leave, no flames or switches, shut the tank valve if safe, call from outside | propane.com; Ferrellgas |
An RV owner, in an AIRLOCK post-purchase survey, wrote: "Sewer smell in RV- flush system out weekly and put enzymes in to make it smell better and does not work." When treatments don't touch the smell, work through the mechanical causes below.
RV toilet smells when flushed: the black tank vent
Dometic's troubleshooting table lists a plugged tank vent as the first cause of odor when the flush valve is open. The fix is to clear the obstruction, following the tank owner's manual. On most RVs that means checking the vent pipe cap on the roof for anything sitting in or over it.
The second cause Dometic lists is the tank contents themselves, and its remedy is a tank deodorant. Dometic also recommends adding water to the bowl before flushing solids and toilet paper.
Watch the roof fan, too. A reply on the Forest River Forums points out that running a strong vent fan with no window cracked can create negative pressure in the RV and draw air in through a faulty valve. If the smell only shows up with the fan on exhaust, crack a window on the far side of the RV and see if it stops.
RV sewer smell between flushes: the bowl, the seal and the floor
Dometic's manual says that to keep tank odors out of the living space, about 1 in. (24 mm) of water should stay in the toilet bowl. On its 300 series toilets, pressing the flush pedal part way adds water to the bowl while the flush ball stays closed.
If the water keeps draining away, the flush ball seal is the suspect. Dometic notes that mineral deposits from hard water can build up on the ball or seal and cause a slow leak, so clean both periodically. For a seal that has lost its shape, Dometic's reconditioning steps are:
- Hold the flush ball fully open by pressing the pedal.
- With a finger, press down with moderate pressure around the edge of the ball seal.
- Close the flush ball.
- With the ball closed, pour one quart of hot tap water into the bowl.
- Let the water cool completely, then check for a leak.
If it still leaks, Dometic says to replace the flush ball seal. Smell with the valve closed and water in the bowl can also come from a damaged floor flange seal under the toilet, which means pulling the toilet and replacing the seal.
These steps are from Dometic's manual for its 300 series gravity toilets. Other toilet brands and models work differently, so check the manual for the toilet in your RV.
Sewer smell from the sink or shower
Sink and shower drains run to the gray tank, and each one has a trap that holds a little water as a barrier. Daisy RV, an RV dealership, explains that when an RV sits unused, that water can evaporate, and tank odor comes straight up the drain. Running water into the drain refills the trap. If the smell improves, a dry trap was the problem.
The next suspect is the air admittance valve, a small one-way vent usually under the sink. RV Enthusiast describes how it opens to let air into the drain line while water flows and closes when the flow stops. When it doesn't close fully, gray tank odor escapes around the sink and spreads through the RV. Daisy RV suggests opening the cabinet and smelling near the plumbing; if the odor is stronger in there, the valve or a fitting is the likely source. RV Enthusiast's fix is replacing the valve.
Daisy RV also says a blocked gray tank roof vent can push odor back through the sink plumbing instead of venting it outside.
What to put in an RV black tank for smell
An RV owner, in an AIRLOCK post-purchase survey, described one version of this: "Smell from black tank on a hot day". Unique Camping + Marine, an RV supply retailer that sells tank treatments, says "hot tanks are the leading cause of stinky black tanks" and that fresh water in the tank cools it down and works as an odor barrier.
Dometic's remedy for odor from the tank contents is a tank deodorant, and its manual lists deodorant products by name. Unique Camping + Marine adds two water habits: keep the black tank valve closed unless you're actively dumping, even on full hookups, and add water to the toilet bowl before use and after every flush, which it describes as a vapor barrier. Follow the directions on whichever treatment you use and keep the vent clear.
AIRLOCK doesn't sell a tank treatment, and no AIRLOCK product goes in the tank. A treatment works on what's in the tank. It won't stop smell getting past a dry bowl, a worn seal or a stuck valve, so check those too if the smell doesn't change.
Why does my RV smell like rotten eggs?
Treat a rotten egg smell in the air as a possible propane leak until you know otherwise. Propane has no smell of its own, so suppliers add a chemical called ethyl mercaptan, which Ferrellgas describes as smelling similar to rotten eggs or a skunk.
If you smell gas, propane.com's safety steps are:
- No flames or sparks. Put out smoking materials and open flames. Don't operate lights, appliances or phones.
- Leave the area immediately and get everyone out.
- Shut off the gas at the tank's main valve if it's safe to do so. Turning it to the right (clockwise) closes it.
- Report the leak from a safe distance: call the propane retailer, or 911 or the fire department if you can't reach them.
- Don't go back until a propane retailer, emergency responder or qualified technician says it's safe, and have the whole system checked before using propane appliances again.
Ferrellgas also recommends propane leak detectors near appliances and low to the ground, where propane collects. For detectors, alarms and what to do if one goes off, see RV carbon monoxide and propane safety. No air purifier or odor product is the fix for a gas smell.
RV water smells like rotten eggs
If the smell only comes from the hot water, the water heater is the likely source. Suburban's water heater guide says many water supplies contain enough sulfur to produce an odor like rotten eggs, often called sulfur water, and that it is not harmful, only unpleasant. Suburban's fix is to chlorinate the water system: add about 6 ounces of household liquid bleach per 10 gallons in the fresh water tank, run it through each faucet until you smell chlorine, let the RV sit a few days, then flush with fresh water until the chlorine is gone. If the smell continues, Suburban says to flush again and replace the anode rod as necessary.
The smell left in the air after the plumbing is fixed
Once the vent, bowl, seals and traps are sorted, some smell can hang in the air, in the bathroom, and in the storage bay where the sewer hose rides. AIRLOCK works on that leftover smell as a system. None of these products fixes a vent, seal, trap or valve, and none of them replaces the checks above.
**AIRLOCK One RV, first, for the whole RV.** One RV is the RV air purifier that works through the rooftop AC. It mounts at the AC intake, ducted or non-ducted, one unit per AC, and eliminates odors in the air the AC moves whenever the fan runs, cooling or not. Tank odors are one of the smells the product page names. It needs 100-240V AC at the rooftop unit, from shore power, a generator or an inverter, and it doesn't work with 12V or 48V DC rooftop AC units. It installs in 15 minutes, usually from inside the RV. Give it a few days of fan time.
Robbie W., an RV owner using AIRLOCK One, wrote: "Works great in about 3 days the tank odors were gone." Ricky S., another owner, wrote: "AIRLOCK One is a great solution to get rid of RV tank odors and the many scents of cooking."
**AIRLOCK Voyage RV, alongside, in the bathroom.** The bathroom is where tank smell starts and where air sits still with the door closed. Voyage RV sets on the counter or a shelf, runs from a 12V socket or a wall outlet, and has an odor removal range up to 4 ft. It works with One RV, covering the one room that needs extra help.
**AIRLOCK OdorGuard in the sink cabinet and the sewer hose bay.** Closed cabinets and storage bays get almost no airflow. OdorGuard's coconut shell charcoal traps odors in the space it sits in, with no power and no fragrance. Recharge it in direct sun for 3 hours once a month, and replace it every 4 to 6 months.
| AIRLOCK One RV | AIRLOCK Voyage RV | AIRLOCK OdorGuard | |
|---|---|---|---|
| Covers | The air its rooftop AC moves through the RV (one per AC) | One small zone, odor removal range up to 4 ft | The closed space it sits in |
| How it runs | Installs at the AC intake; works whenever the fan moves air | Plug-in; 12V DC car plug or 100-240V AC adapter | No power; coconut shell charcoal, recharged in the sun |
| Where it goes | At each rooftop AC | Bathroom counter or shelf | Bathroom sink cabinet, sewer hose bay |
| Fixes plumbing? | No | No | No |
For how the ionization works, see how AIRLOCK works. For other smells, such as cooking, pets and smoke, see the best RV odor eliminator, by smell.
When it still smells after all of this
If the vent is clear, the bowl holds water, the seals are good, the traps are full and the tank has been dumped and flushed, but the RV still smells, the odor has likely soaked into soft goods or is lingering from before the fix. That's covered in why an RV black tank still smells after cleaning.
RV sewer smell FAQ
Why does my camper smell like sewer?
The usual causes are a plugged black tank vent, too little water in the toilet bowl, a worn flush ball seal or floor seal, a dry sink or shower trap, or an air admittance valve that won't close. Work through them in that order, using the table above.
Why does my RV toilet smell when I flush?
Dometic lists two causes of smell while the flush valve is open: a plugged tank vent and odor from the tank contents. Clear the vent and add a tank deodorant. If the roof fan is running on exhaust with every window shut, crack a window and try again.
What can I put in my RV black tank for smell?
Use a tank deodorant or treatment, which is Dometic's remedy for odor from the tank contents. Add water to the bowl before flushing solids too. If the smell doesn't change, check the vent, the bowl water and the seals, because a treatment can't fix those.
What's the best RV toilet smell remedy?
Match the remedy to the cause. Keep about an inch of water in the bowl, clean or recondition the flush ball seal, clear the vent and use a tank deodorant. Once the plumbing is right, AIRLOCK One RV on the rooftop AC works on the smell left in the air, with Voyage RV in the bathroom and OdorGuard in the sink cabinet.
Why does my RV smell like rotten eggs?
Treat it as a possible propane leak first. Propane is odorized with ethyl mercaptan, which smells like rotten eggs. Get everyone out, avoid flames and switches, shut the tank valve if it's safe and call the propane retailer or 911 from outside.
Why does my RV water smell like rotten eggs?
If only the hot water smells, the cause is usually sulfur water in the water heater. Suburban says it isn't harmful and recommends chlorinating the water system, flushing it and replacing the anode rod as necessary.
Is a rotten egg smell in an RV dangerous?
It can be, because propane smells like rotten eggs by design. Follow propane.com's steps (leave, no flames or switches, shut off the gas if safe, call from outside) and don't go back in until a qualified person says it's safe. A rotten egg smell from the hot water only is usually sulfur water, which Suburban says is not harmful.
Will an air purifier get rid of sewer smell in an RV?
Only the smell left in the air after the source is fixed. An air purifier can't seal a vent, a trap or a toilet. Once the plumbing is right, AIRLOCK One RV eliminates the leftover odor in the air the rooftop AC moves whenever the fan runs, and Voyage RV can sit in the bathroom alongside it.