If you've flushed and treated the black tank, checked the seals and your RV still smells, the odor that already got inside the RV is hanging on in the air and in the soft goods. Cushions, curtains, carpet and bedding soak up odor and release it slowly, so the smell keeps drifting back into the air after the tank work is done.
That's why another round of flushing or enzymes often doesn't change it. 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." Another described an "Odd funk odor inside and under rv. Have been flushing tanks to see if that is the culprit." A customer in an AIRLOCK post-purchase survey named "high heat in Texas causing black tank odors inside RV even with excessive cleaning."
Before working on the smell that's left, make sure nothing is still letting tank odor in.
Already did these?
If you've already done all of these and the RV still smells, the problem is the odor that's already inside, which the next section covers.
- Flushed and treated the black tank. Dometic's toilet manual lists a holding tank deodorant as the remedy for odor from the tank contents.
- Cleaned the gray tank. Daisy RV, an RV dealership, says a gray tank can need cleaning and flushing just like a black tank, because dumping doesn't always remove the residue stuck inside.
- Checked the valve seals. RV Enthusiast found that when the seal on the air admittance valve under the sink turns brittle, tank gases can permeate the RV, and the fix is a new valve.
- Cleared the roof vents. Dometic lists a plugged tank vent first among the causes of odor while you flush.
- Replaced the toilet seal. Dometic points to a damaged floor flange seal when the smell shows up with the flush valve closed and water in the bowl.
- Refilled the P-traps. Daisy RV explains that trap water can evaporate when an RV sits unused, and running water into each drain refills it.
Some signs point to a source that's still open. Daisy RV says a smell that's strongest at a drain or inside the sink cabinet points to the trap, the valve or a fitting, and a smell that returns quickly after you run water into a drain means something besides a dry trap. A reply on the Forest River Forums warns that a strong roof vent fan running with no window cracked can create negative pressure and draw air in through a faulty valve, so a smell that only shows up with the fan on is worth chasing.
A rotten egg smell is a different problem. Treat it as a possible propane leak and follow the steps in the FAQ below before anything else.
Why the smell hangs on after the tank work
Odors soak into soft, porous materials like cushions, curtains, carpet, bedding and the headliner, and those materials give the smell back slowly. With the door and windows shut, that smell builds up in the cabin air again, which is why the RV can seem fine after airing it out and smell like the black tank the next time you open the door. The rooftop AC moves that same air every time the fan runs.
How to clear the smell that's left
- Air the RV out. Open windows on opposite sides and run the roof vent fan, with a window cracked whenever the fan is on exhaust.
- Wash what comes off. Bedding, curtains, throw rugs and removable cushion covers can go through the wash following their care labels. Hang anything that can't be washed outside to air out.
- Keep the tank habits going. Unique Camping + Marine recommends adding water to the toilet bowl before you use it and after every flush, which it describes as a vapor barrier, and keeping the black tank valve closed until you dump.
- Treat the air. AIRLOCK One RV on the rooftop AC eliminates the odor in the air, as covered below.
AIRLOCK One RV eliminates tank odor in the air
AIRLOCK One RV installs at the rooftop AC and eliminates odors in the air the AC moves whenever the fan runs, whether or not the AC is cooling. Tank odors are one of the smells it breaks down instead of covering up with a fragrance.
An RV owner using AIRLOCK One wrote: "Works great in about 3 days the tank odors were gone." Another RV owner using AIRLOCK One described the result this way: "You might be disappointed if you think this is gonna make your RV smell like a rose garden. It doesn't. What it does is make it not smell at all."
One RV treats the air that moves through the AC rather than the fabric itself, so keep airing out and washing soft goods while it works on the air. It also can't fix a plugged vent, a worn seal or a dry trap, which is why the checklist comes first.
A few things to know before you order:
- Install one AIRLOCK One RV per AC unit. A ducted AC that feeds several ceiling vents still counts as one unit, and two ACs need two.
- It works with 100 to 240V AC rooftop units and doesn't work with 12V or 48V DC units.
- Most owners install it themselves in about 15 minutes, usually from inside the RV.
- AIRLOCK One RV is not an ozone generator.
- You can try it for 90 days and send it back if you don't smell the difference.
RV black tank smell FAQ
Why does my RV still smell after I dumped and flushed the black tank?
Odor that already got inside the RV hangs on in the air, and cushions, curtains, carpet and bedding soak it up and release it slowly. Air the RV out, wash what you can, and treat the air. If the smell is strongest at a drain, in a sink cabinet or when you flush, go back through the checklist, because a source may still be open.
Why does my RV smell worse on hot days?
Unique Camping + Marine calls hot tanks "the leading cause of stinky black tanks" and says fresh water in the tank cools it down and works as an odor barrier. Daisy RV says heat makes gray tank smell worse too. An RV owner, in an AIRLOCK post-purchase survey, named the problem as "Smell from black tank on a hot day".
What can I put in my RV black tank for smell?
Dometic's remedy for odor from the tank contents is a holding tank deodorant. Keep water in the bowl and the black tank valve closed until you dump. A treatment works on what's in the tank, so it won't help with smell that's already in the cushions or the air, or with a bad seal or a plugged vent.
How do I get black tank smell out of RV cushions and bedding?
Wash removable covers, bedding and curtains following their care labels, and air out the rest with the windows open. AIRLOCK One RV eliminates odors in the air that moves through the AC whenever the fan runs. It treats the air, so the fabric itself still needs washing or airing out.
Does AIRLOCK One RV cover up the smell?
No. It eliminates odors in the air the AC moves instead of covering them up with a fragrance, and it isn't an ozone generator. It works whenever the AC fan runs, and cooling is optional.
Why does my RV smell like rotten eggs?
Treat it as a possible propane leak. Propane has no smell of its own, so suppliers add ethyl mercaptan, which Ferrellgas describes as smelling similar to rotten eggs or a skunk. propane.com's steps are to put out flames and avoid lights, appliances and phones, get everyone out, shut off the gas at the tank's main valve if it's safe, and call your propane retailer (or 911 or the fire department) from a safe distance. Don't go back in until a qualified person says it's safe. If only the hot water smells like rotten eggs, Suburban's water heater guide says the usual cause is sulfur water, which is not harmful, and recommends chlorinating and flushing the water system and replacing the anode rod as needed.