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SilverCabin · 08-24-2016, 07:00 AM

We're all closed up with the AC running (it's hot here in Florida) and the wife turns on the range hood to vent some cooking smells. I open the wardrobe to get something and there is a black tank smell. I know the smell having made the mistake of flushing the toilet with the vent fan running when everything is closed. The black tank vent pipe is on the other side of the Airstream about four feet from the closet. I open the compartment below the wardrobe, where the pump is and the floor penetrations, and no smell there. We turn the fan off and after a few minutes, the smell goes away. Can't figure out where this is coming from. Any suggestions?

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Dexterpix · 08-24-2016, 07:15 AM

If you are running the vent fan with the camper closed up, air has to be pulled in from some where to replace the air you are venting out the fan. Is it possible you toilet or sink or shower drain is open and you are pulling air in thru the plumbing vent stack, into the camper thru an open drain. I am not sure of your trailer configuration but your shower or sink mite share a vent stack with your black water tank. Running the stove vent will cause you to draw air in from some where. I think the AC's are closed to recirculate interior air to be more efficient so outside air will be drawn in from some place.

Best of luck
Joe D

OTRA15 · 08-24-2016, 07:26 AM

I deleted my recent post because I had not read your original post carefully enough. Sorry.

Is it windy there right now, by any chance, and could a downdraft from a nearby roof line, tree, or other obstacle, be blowing your black tank gases down the vent stack pipe?

Joe's suggestions are sound IMO, especially to make sure all your plumbing traps incl. the shower have water in them.

Good luck!

Peter

SilverCabin · 08-25-2016, 08:13 AM

After further study, I think I may have solved the problem. We had a breeze blowing from the front of the trailer to the rear. The blank tank vent is forward of the refrigerator vent. The refrigerator compartment is next to the wardrobe and there is no airtight seal between them. So the fan, I think, was drawing in the sewer gas through the refrigerator vent into the wardrobe. That's why we only smelled it in the upper part of the wardrobe and not underneath where the floor penetrations are. I was ready to take apart the wall where the vent pipe goes up from below, but now will just wait and see if my theory holds up.

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OTRA15 · 08-25-2016, 08:47 AM

Good call -- thought it might be wind-related.

Al and Missy · 08-25-2016, 10:16 AM

Randy,
I thought I had read that the refrigerator compartment was supposed to be isolated from the trailer interior due to the potential for the fridge generating carbon monoxide. I think it is in the fridge installation instructions.

Al

dkottum · 08-25-2016, 10:48 AM

Quote:

Originally Posted by Al and Missy

Randy,
I thought I had read that the refrigerator compartment was supposed to be isolated from the trailer interior due to the potential for the fridge generating carbon monoxide. I think it is in the fridge installation instructions.

Al

I think you're right, no carbon monoxide, no black tank smells, and no cold air drafts coming in.

Check around the edge of the fridge and see if it is fitting tight against the cabinet it is mounted into.

GandW · 08-25-2016, 01:52 PM

There is a re-vent under the wardrobe on the right hand side for the shower. It is a short stack with a vent on top. The conditions may have been right for it to vent. My 2015 27FB does the same thing sometimes. The thread made me think of what it might be from. Exhausting without an inflow? I know it is the worst when it is hot out. Now I have something to play with.

OTRA15 · 08-25-2016, 02:31 PM

Quote:

Originally Posted by GandW

There is a re-vent under the wardrobe on the right hand side for the shower. It is a short stack with a vent on top. The conditions may have been right for it to vent. My 2015 27FB does the same thing sometimes. The thread made me think of what it might be from. Exhausting without an inflow? I know it is the worst when it is hot out. Now I have something to play with.

That's the ticket --an excellent observation!

Welcome to the forum, and thanks for this insight.

Peter

OTRA15 · 08-28-2016, 06:38 AM

Wondering if you have seen the recent comment from GandW about the hidden vent, and whether it might apply to your AS? Thanks.

Quote:

Originally Posted by SilverCabin

After further study, I think I may have solved the problem. We had a breeze blowing from the front of the trailer to the rear. The blank tank vent is forward of the refrigerator vent. The refrigerator compartment is next to the wardrobe and there is no airtight seal between them. So the fan, I think, was drawing in the sewer gas through the refrigerator vent into the wardrobe. That's why we only smelled it in the upper part of the wardrobe and not underneath where the floor penetrations are. I was ready to take apart the wall where the vent pipe goes up from below, but now will just wait and see if my theory holds up.

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SilverCabin · 08-29-2016, 06:39 PM

After reading the posts above, I took a closer look at the wall between the refrigerator and the wardrobe. There is a gap at the top of the wall, but the is some kind of weather stripping stuffed into the gap, so I believe the refrigerator compartment is sealed off from the trailer interior. It also is fitting snug at the front, so there goes my theory.

I found the re-vent for the shower below the wardrobe. It's in the compartment below the wardrobe. There is no smell coming from that, and as I said before, there is no smell at all that I can detect in that compartment even though that's where the vent is and there are several floor penetrations for the plumbing. The main gray water vent stack is across the hall from the re-vent, and the black tank vent is separate from the gray water vent stacks, and about three to four feet forward.

I was able to reproduce the problem by opening the shower overhead vent and turning on that fan while the trailer was closed up because the AC was running. After a few minutes, we could detect the smell in the wardrobe, in the center section where the hanger bar is, not in the area at the top above the shelf, and again, not below where the re-vent lives and all the plumbing.

Frankly, I'm stumped on this.

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OTRA15 · 08-29-2016, 07:13 PM

Thanks for the update!

Good luck chasing this down.

Peter

burnsdl · 01-30-2017, 07:52 PM

We are currently having the same issue in our (2012) 27fb. Is anyone willing to provide an update to their situation?

Thanks, _dave

truxpin · 01-30-2017, 08:37 PM

Just a thought... Have you checked to see that the black tank vent pipe is actually protruding up & out the top of the roof? (and that there is some form of sealant around the pipe?
We had a similar issue and found the black vent pipe was about an inch below the outer roof skin AND didn't have any barrier wrapping around it. Vent fans or the right breeze caused reverse airflow into the trailer and sometimes the AC units would pull black tank fumes through the inner/outer skin airspace. Unscrew the vent caps on the roof and visually verify the vent pipes are protruding an inch or two.....And have sealant with no gapping around them..

GandW · 01-31-2017, 05:26 AM

Since I posted the one about the revent, we have been full timing for 3 months. We leave one Fantastic fan vent open and have never had the smell again in the closet. IMO if you leave everything closed up and then use an exhaust fan, it has to suck from somewhere.

Oh yeah, the one to leave open is the one away from the tank vents. When the wind was blowing just right one time , the entire AS smelled like the inside of the black tank.

glcmranger · 01-31-2017, 06:36 AM

It probably is the Air Admittance Valve (AAV). Go to Amazon, search on this item:
"Ayrlett AT-500 Air Admittance Valve 20 DFU with ABS and Threaded Adapter Configuration, 2"-1-1/2", Black".

Rich W · 01-31-2017, 06:58 AM

I found 3 of those valves in our 23' AS; one under the kitchen sink (frozen on, afraid to put anymore pressure on it for fear of it breaking), one under the bath vanity (directly under the vanity top. I'd have to remove the entire vanity to be able to replace the valve; wonderful engineering.) and one in the rear storage compartment, under the bed, where we smell the tank the worst. Changing this valve had no effect.

We stopped using ours for #2 and use some of the deodorant tablets available at Wal-Mart. That has helped the most. A little bleach in the bath vanity about every month helps too.

When we travel long distances I put some holding tank cleaner in the black tank and let it slosh around, then dump when we arrive, at least 200 mile trips. The longer the better. Dump and flush with fresh water.

Boxite · 01-31-2017, 09:20 AM

Folks, those auxiliary vents are for the purpose of admitting air into the sewer system....they do not ordinarily contribute to the stinky smell due to running vent fans.*

If you download and examine the plumbing schematics for your model trailer you will discover that the gray tank and the black tank SHARE the black tank vent that goes up thru the roof. They usually "T" together just above the black tank.

If you run an exhaust fan...either the Fantastic Fan OR the range-hood exhaust ....with the trailer all closed up...that exhausted air MUST BE REPLACED...and with the windows all closed ...guess where that air must come from...??? It comes down the black tank vent on top of your roof....gathering all those sweet smells...and then enters the gray-tank vent at the "T"...and comes into your trailer thru the sink drains and the shower drain...*unless you have them plugged....and THEN* the aux vents pop open to relieve the vaccum and admit that stinky air into the cabinets and wardrobes, etc.

SOLUTION: Open a window when running exhaust vents or Fantastic Fans.

Rich W · 01-31-2017, 09:37 AM

We had smell with no fans on and only towards the rear of the trailer. When I go to the trailer while it's been in storage for a month, there's a smell, well, if we don't treat the tanks there's a smell. We learned early on about not having a window or door open, first trip I think.

Maybe we're just super sensitive but mostly the smell seemed to have been coming from the rear where the bed and toiler are. That's why I replaced that valve, it didn't help. After using a black tank treatment and driving about 300 miles, using the deodorants from Wal-Mart and using the CG facilities for #2, life is better.

Minno · 01-31-2017, 10:14 AM

We had an issue last summer with black tank smell in our bathroom. Found out our toilet flange bolts were broken. Replaced those, and the smell was better, but not good. Found out our vent stack was plugged just above the black tank. Once we cleaned it out with water and a drain snake, no more smell. You might need to check to make sure your stack isn't plugged. The sewer gasses have to go somewhere....

Kay