It stinks!

[Fffrank]

Have been chasing this problem and feeling defeated. My rig STINKS while driving. Sometimes worse than others but it's obvious I've got a black tank smell coming from somewhere. The solution is to stop and dump but it's not always convenient. The frustrating part is I keep thinking I've solved the problem -- but there's no way to test until we camp again, get the tank partially filled and then start to drive. Thus it's been a lengthy process.

Have removed W/D drain plumbing and installed a rubber cap. No difference. Although my nose tells me that the problem is likely coming from that area.

Have removed vent cap from the roof and it didn't appear there was any nests or debris inside the pipe? Have resealed the vent pipe to roof connection and also verified there does not appear to be any "fresh air" leak in the interior area where this pipe passes through.

I don't believe the smell would be coming from the grey tank -- but I suppose it's possible?

Any ideas on next places to start?

[Spk64]

AAV drain vents are a know failure point. Look under each sink and you may have one. You can put a plastic bag over to seal up and test for odor. Then replace with a higher quality unit from any big box store. I would also consider replacing the vacuum breaker if you have one for the black tank rinse.
To rid our Coach of odors I replace the AAV ‘s, vacuum breaker and also put Cyclone vent caps on. We no longer have any odor issues while stationary or moving regardless of how full tanks are.

[MSHappyCampers]

What about the air admittance valve under the lavatory?

[CLIFFTALL]

The grey tank is a real possibility. We always shut the water off, put drain plugs in the sinks and covered the shower drain as well. After the first time that we experienced what you’re relating to we never had another issue.

[TXiceman]

The gray tank can smell worse than the black tank. One very commons source of the smell is the air admittance valve which is locate near the kitchen sink and the bathroom sink.
AAV

Take your pick of them. You can usually pick these up at a local hardware store. They are usually installed only hand tightened. To see if that is the source of the small you can tape one up for a trial.

Another common source of a bad smell is the battery getting dry or over charging. Check the batteries.

Ken

[Ljwt330]

Originally Posted by Fffrank

Have been chasing this problem and feeling defeated. My rig STINKS while driving. Sometimes worse than others but it's obvious I've got a black tank smell coming from somewhere. The solution is to stop and dump but it's not always convenient. The frustrating part is I keep thinking I've solved the problem -- but there's no way to test until we camp again, get the tank partially filled and then start to drive. Thus it's been a lengthy process.

Have removed W/D drain plumbing and installed a rubber cap. No difference. Although my nose tells me that the problem is likely coming from that area.

Have removed vent cap from the roof and it didn't appear there was any nests or debris inside the pipe? Have resealed the vent pipe to roof connection and also verified there does not appear to be any "fresh air" leak in the interior area where this pipe passes through.

I don't believe the smell would be coming from the grey tank -- but I suppose it's possible?

Any ideas on next places to start?

Just to start, the grey tank odor can be as foul as the black tank and much more likely to enter the interior of the coach.

Every drain from a sink or W/D is a potential odor producer. Most common cause is the air admittance valve (AAV) on each drain from the sinks or washer. It prevents a vacuum from forming in the line as water flows through by allowing air to enter. It's supposed to close and prevent odors from the tank from exiting into the surrounding air. Those valves are typically cheap and fail to seal, allowing odor to enter the coach. I strongly suspect that is your problem.


These valves will be found under each sink, on a vertical riser after the p-trap. The riser will be at about the level of the sink bottom. Simply replace the valve, found at nearly any hardware store. Your W/D drain should also have one, but you may need to look hard due to the location of the stand pipe and p-trap.


The p-traps are also a source, but it doesn't sound like the water is being drawn out. Still, be sure each trap is full of water before you drive off.


Odors from the black tank are rare as the only point of entry is usually the toilet. If the bowl has water and the seal is sound, it is unlikely the odor is from the black tank. Still, you cannot eliminate it completely, but I wouldn't suggest you try until you assess the condition of the grey tank drains and AAV.

[Fffrank]

Thanks, all -- I removed the AAV from the washer/dryer plumbing system but it did not occur to me that they could have also been a problem on the kitchen/bath systems. Interesting that the grey tank may in fact be the issue. I'll replace as these are very cheap and easy to access.

I know what a bad/over-charging battery smells like. It is not that smell.

Really appreciate all the good replies!!

[JerKat2]

Had the same issue years ago on our first ever trip in our coach. It was the gray tank and turns out that the P-traps had dried out during storage allowing the odor to come back into the coach.

Before each trip now, I run some water in each sink drain and the shower just to make sure the traps are filled. Never had the issue since then. Could be that simple or could be the AAV’s, or …..

Hope you get it figured out, cause I know personally that it does stink.

[Fffrank]

Originally Posted by Spk64

I would also consider replacing the vacuum breaker if you have one for the black tank rinse.

I don't think I have one of these? Does anyone know where it might be located?

[JJTL]

Do you have a washer/dryer??

Every so often we will arrive at camp and the water in the washer/dryer p-trap has been lost. Smells quite bad.

We simply remove the access panel above the unit and pour a cup of water down the drain to restore the seal. Works like a charm.

If you have one, pour some water down the drain and see if that helps. Can’t hurt!

All the best!
Josh

[Kurt Averill]

Mine only smelled when traveling, but it was pretty foul. I didn't suspect the toilet as it would hold water. I rebuilt the toilet - new seals and valve - l Haven't had an issue since. The vacuum breaker for the black tank flush on mine was right above the tank curbside - under the bathroom lav. no issue with it though.
I have not had issues with gray tank odor as we are careful to keep food waste out of the grey tank.

[Spk64]

Originally Posted by Fffrank

I don't think I have one of these? Does anyone know where it might be located?

Mine was located under sink in bathroom.

[Fffrank]

Originally Posted by Spk64

Mine was located under sink in bathroom.
Attachment 336706

Awwww -- I do have one of those! It's hooked to a red PEX line so I assumed it had something to do with hot water.

[Fffrank]

Originally Posted by Kurt Averill

Mine only smelled when traveling, but it was pretty foul. I didn't suspect the toilet as it would hold water. I rebuilt the toilet - new seals and valve - l Haven't had an issue since. The vacuum breaker for the black tank flush on mine was right above the tank curbside - under the bathroom lav. no issue with it though.
I have not had issues with gray tank odor as we are careful to keep food waste out of the grey tank.

Toilet was rebuilt this winter. It does hold water -- and doesn't seem to be any smell in my toilet room.