Sewer odor coming from bathroom sink

[btf66509]

I have a 2016 Wildcat 29RKP, and have always had a problem with sewer odor coming up through the bathroom sink, and maybe the shower too (it’s hard to tell). It doesn’t always smell, mostly right after towing or after dumping tanks. I also sometimes get a terrible sewer odor from the front A/C, I’m guessing it’s pulling the odor from the roof vent. It’s like the black and gray systems are somehow connected and gasses are flowing from one to the other. Is this a possibility? Thanks for any help!

[A32Deuce]

If after towing, put water in the traps same with after dumping. I found with ours after towing and sometimes, enough water will drain out of the p traps enough to allow for the smell. See if that works for you.

[Cypressloser]

I'm assuming this happens even with the grey tanks closed.
The AC should not pull air in from outside but it could cause enough of a stir to pull smells through the air admittance valve under the sink if not sealing properly or the Hepvo valve under the shower. Also, make sure you always have water standing in the toilet bowl.

[TranceX2]

I usually put some black water holding tank treatment chemical down my sink and shower drains after I drain all my tanks and it always takes care of the smell problem.

I also found I get tank odor if I run the bathroom fan without cracking a window somewhere in the camper.

[RMWSierra]

Little Pinesol in grey tank.

[amblt]

Originally Posted by btf66509

I have a 2016 Wildcat 29RKP, and have always had a problem with sewer odor coming up through the bathroom sink, and maybe the shower too (it’s hard to tell). It doesn’t always smell, mostly right after towing or after dumping tanks. I also sometimes get a terrible sewer odor from the front A/C, I’m guessing it’s pulling the odor from the roof vent. It’s like the black and gray systems are somehow connected and gasses are flowing from one to the other. Is this a possibility? Thanks for any help!

Recently had same problem in our seasonal trailer. This works for us:


Keep plugs in all basins and showers except to drain the water. (directly related to next point).



Keep the traps full (evaporation during extended absences is a problem).


Use a tank treatment (I like TST Orange) after each tank dump. I use the same dosage rate as for the black tank-the cost is not that great.


Cheers

[Bama Rambler]

Have you ever checked the Air Admittance Valve under the sink?

If they stick open (which is common) they allow holding tank gasses back into the RV.

[garbonz]

Waterless traps, which you may have, can get stuff, like hairballs in them and won't seal, and a P trap can dry out. Either way can result in odors.

Waterless traps can be disconnected and cleaned, same with P traps.

[jimmoore13]

At the 30,000 foot level:

1. Dry traps admit odor from beyond the trap. Your traps could partially empty from air draft over tank/drain vents. Close your sink stoppers tightly, and that may help prevent the suction over the gray-tank vent(s) from pulling water out of the traps while going down the road. Closing the stoppers will also curtail evaporation from the traps when the RV is idle. I have a floor drain in my laundry room that must be topped off about once every two weeks or the stench is something to behold! Refill the traps ASAP on arrival (both at your destination and at home), and even if there is a bit of odor, it will dissipate quickly.
   Sewer odor from the toilet, however, would warrant refreshing the seals on the flush valve. There is no trap on the toilet in most RVs.
2. Depending on the location of your AC and your black-tank vent, it's easy to believe that your AC is inhaling sewer gas from your roof vent. At my home, the sewer vent is generally upwind of my deck with predictable results. I purchased a charcoal filter for the sewer vent, and it works quite well. This one is just representative...I like that it comes in many sizes. The one I chose for home was different. We have a 3" pipe for the sewer vent. Pick one that has replaceable charcoal bags. They eventually stop working, and a $6 replacement works wonders.
3. In the "heat of the moment," if your AC has the ability to exclude outside air (recirc), that might provide temporary relief, but that's not an answer....

[CedarCreekWoody]

Originally Posted by Bama Rambler

Have you ever checked the Air Admittance Valve under the sink?

If they stick open (which is common) they allow holding tank gasses back into the RV.

X2

This is a common problem. For some reason people seem reluctant to do a simple check. A search on AAV in the forum will provide lots of info.

[Nigels]

I tried the commercially available tank additives with mediocre success. I now use granulated chlorine for my grey tanks, the type you put in your swimming pool, its cheap and a tablespoon full is all you need it will keep your tanks smelling good in the warmest of weather.
I have not had a problem with the black tank as it is easy to dump and flush as often as needed, (we only glamp, no dry camping for the admiral), so with full hook up that is easy to do.

[btf66509]

Thanks for all the replies everyone! I’ve looked under the sink for the AAV before and don’t see it, just the PEX lines. I’m sure it’s somewhere, just don’t know where. I’ll try the other suggestions too.

[Bama Rambler]

The Air Admittance Valve will be right up against the bottom of the counter top. And it'll most likely be near the rear of the cabinet.

[btf66509]

Thanks Bama, I’ll look again.

[Lovestogo]

We encountered this experience this past weekend while camping of the smell coming up from the gray tank. I remembered reading about the AAV and immediately got my phone and found it on this forum. We didn’t have one under the kitchen sink but did have one underneath the bathroom sink. Hubby pecked on it and the smell disappeared. Next time we ran water in the bathroom sink, there was the smell back.

This is what ours looked like underneath the sink. Found a replacement at Lowes in the plumbing section for $6.17. We opted for the one that was made by Oatey and it was around $25. Had to get an adapter to go with it.

The black one is the one that came with the camper. The white one is the replacement which we still have to install.

[Lovestogo]

Originally Posted by Lovestogo

We encountered this experience this past weekend while camping of the smell coming up from the gray tank. I remembered reading about the AAV and immediately got my phone and found it on this forum. We didn’t have one under the kitchen sink but did have one underneath the bathroom sink. Hubby pecked on it and the smell disappeared. Next time we ran water in the bathroom sink, there was the smell back.



This is what ours looked like underneath the sink. Found a replacement at Lowes in the plumbing section for $6.17. We opted for the one that was made by Oatey and it was around $25. Had to get an adapter to go with it.



The black one is the one that came with the camper. The white one is the replacement which we still have to install.

Can someone help me? We’ve had to return what we purchased and all I can find is air admittance valves that have male threading on the outside. My DH is telling me ours needs to be female threaded. We’ve looked for an adapter female to female and can’t find one. For those who have replaced their air admittance valves under the bathroom sink, could you please give me your insight and guidance? This is on a 2017 Rockwood Mini 2104s.

[jimmoore13]

Originally Posted by Lovestogo

We encountered this experience this past weekend while camping of the smell coming up from the gray tank. I remembered reading about the AAV and immediately got my phone and found it on this forum. We didn’t have one under the kitchen sink but did have one underneath the bathroom sink. Hubby pecked on it and the smell disappeared. Next time we ran water in the bathroom sink, there was the smell back.

This is what ours looked like underneath the sink. Found a replacement at Lowes in the plumbing section for $6.17. We opted for the one that was made by Oatey and it was around $25. Had to get an adapter to go with it.

The black one is the one that came with the camper. The white one is the replacement which we still have to install.

Thanks for this.
Interestingly, all drain vents in my PUP go to the outside...even the shower has one (photo). I would not have expected an "instavent" on a factory install. Live and learn.

P.S. I normally mostly drain my grey-water tank before traveling, because a hard right turn combined with a nearly full grey tank yields spew out the shower drain vent. Kind of embarrassing and potentially suspicious to following traffic (e.g. cops).

[CedarCreekWoody]

Originally Posted by Lovestogo

Can someone help me? We’ve had to return what we purchased and all I can find is air admittance valves that have male threading on the outside. My DH is telling me ours needs to be female threaded. We’ve looked for an adapter female to female and can’t find one. For those who have replaced their air admittance valves under the bathroom sink, could you please give me your insight and guidance? This is on a 2017 Rockwood Mini 2104s.

Amazon lists several models with female threads and most hardware stores carry them as well.

[jimmoore13]

Originally Posted by Lovestogo

Can someone help me? We’ve had to return what we purchased and all I can find is air admittance valves that have male threading on the outside. My DH is telling me ours needs to be female threaded. We’ve looked for an adapter female to female and can’t find one. For those who have replaced their air admittance valves under the bathroom sink, could you please give me your insight and guidance? This is on a 2017 Rockwood Mini 2104s.

You may be able to find the right "instavent", but if all else fails, Fernco makes many adapters that can do the job. And these are first class solutions. Fernco devices meet code.