Black tank vent stack clogged

[Re-Pete]

We've been noticing lots of odor coming from the toilet every time it's flushed. I got up on the roof and put a light into the vent stack and I see water reflected about 10 or 12" from the top opening. A PO secured screen over the opening which I can't remove and replace without removing the cast aluminum TeePee, which is riveted and well sealed to the roof. Has anyone encountered this issue. Any suggestions on how to correct it without putting a hole in the screen and snaking it?

[Protagonist]

Go ahead and cut the screen. You can buy screen patch kits on Amazon, and at places like Home Depot or Lowe's if you feel there's value in keeping a screen over the opening. If you don't feel there's value added by the screen, just cut it all off (where it's accessible) and be done.

[Roadhoop]

Only two obvious ways for water to be that high in the vent. Bottom up from below (overfill of black tank) or top down from above (leak in vent). I would not only fix the clog, but understand how it happened.

[dznf0g]

To my knowledge, AS puts no screen on the stacks (nor most other mfrs). Mine just has a cap/deflector on it and I have no issues with stuff getting in. remove the screen and probe.

[dznf0g]

I installed one of these to replace the OEM plastic cap.

http://www.homedepot.com/p/DANCO-Ste...182X/100577437

[overlander63]

Originally Posted by dznf0g

To my knowledge, AS puts no screen on the stacks (nor most other mfrs). Mine just has a cap/deflector on it and I have no issues with stuff getting in. remove the screen at probe.

That's incorrect. Airstream has put screen over vents to help prevent foreign objects, such as insects, out of the vent pipes.

[dznf0g]

Originally Posted by overlander63

That's incorrect. Airstream has put screen over vents to help prevent foreign objects, such as insects, out of the vent pipes.

Huh, mine didn't have one. Of course I should have known that the only consistency with AS over the years is inconsistency. My old SOB didn't have one either.

[Protagonist]

Originally Posted by Roadhoop

Only two obvious ways for water to be that high in the vent. Bottom up from below (overfill of black tank) or top down from above (leak in vent). I would not only fix the clog, but understand how it happened.

No. That much water column in the vent stack doesn't happen from below, because the toilet doesn't pump water upwards. Even if the black tank overflowed, the water level in the stack couldn't get any higher than the toilet rim. You'd know right away when the toilet didn't flush.

Since presumably the toilet does flush, the water had to come from above and got trapped by a clog.

Obvious suggestion, empty the black tank and check the vent again to see if the water level in the vent stack changes. Since the vent stack is clogged, hold the toilet valve open while the black tank is emptying, to let air into the tank to replace the water that is flowing out.

And obvious question, since the vent stack is clogged and there's a screen over the vent, where did the clog come from? THAT might have happened from below, meaning the whole vent is full of rainwater top to bottom.

[dznf0g]

Originally Posted by overlander63

That's incorrect. Airstream has put screen over vents to help prevent foreign objects, such as insects, out of the vent pipes.

I see now that Pete has a '92. IS this one of the aluminum "squareish" collars with no cap? I seem to recall they had a screen.

[Glenritas]

Originally Posted by dznf0g

To my knowledge, AS puts no screen on the stacks (nor most other mfrs). Mine just has a cap/deflector on it and I have no issues with stuff getting in. remove the screen and probe.

The O.P. has a 1992 Excella , It has an aluminum stack "cover" with a gasket
that is riveted to the roof over the vent pipe.
BTW if the gasket fails it will let water in between the outside and inside panels that will run down to the floor via the c channel and cause the floor to rot.

My 1969 Tradewind has a "plastic" cover with a screen riveted to the roof.

Both of these "covers" are open to the sky and can have stuff fall in and down the pipe .
I found a wasp nest in mine.
I also found in my original bath vent mud dubber nests above the filter.

[Protagonist]

Originally Posted by Glenritas

The O.P. has a 1992 Overlander , It has an aluminum stack "cover" with a gasket
that is riveted to the roof over the vent pipe.
BTW if the gasket fails it will let water in between the outside and inside panels that will run down to the floor via the c channel and cause the floor to rot.

Mostly preventable by drilling a small drain hole in the side of the cover at the lowest point of the cover above the roof line (and above the gasket). Give the rainwater someplace to go other than through the gasket.

[cazual6]

Originally Posted by Roadhoop

Only two obvious ways for water to be that high in the vent. Bottom up from below (overfill of black tank) or top down from above (leak in vent). I would not only fix the clog, but understand how it happened.

I concur. Patch while on the road to get you going, but always get to the root cause of the problem.

[Re-Pete]

Thanks for the insights, suggestions, and encouragement. To further clarify, the collar looks like the 1st pic posted by Glenritas. The tank is definitely not anywhere close to full.

Just last week we flushed the black tank very thoroughly using a tank spray wand inserted through the toilet.

Naturally if the water in the stack is 10 to 12" from the top then it's not the result of a full tank. If that were the case odor would be the least of our problems since we'd be under water inside the AS, and black water at that. Haha. I guess the upside would be knowing we were water tight.

I don't understand how this might be caused by a leak in the vent stack, but maybe I'm misunderstanding the suggestion. My guess is a clog below maybe where it reaches the tank, caused by god knows what. Really not sure how long it's been an issue, but I'm guessing it's been awhile since it is full of water.

Looks like I'm going to have to puncture the screen, which I hate doing because to repair it I'm going to have to take up a lot of caulk and remove the collar to redo it. I can tell a PO put the screen on as it's nylon and held in place with aluminum tape. And there is not sign of a gasket, just a lot of quality whiteish caulk. Right now my snake is 150 miles away, but I'll be where it is in a couple of weeks and I'll fix it then. I was hoping someone knew a better easier way. Haha. I'll post my results and if I learn something about the cause or probable cause I'll post that as well.

Thanks,
Pete

[AlinCal]

I can tell you the vent in my 91 has two 90 degree bends just below the roof were it offsets to get in the corner of the bath wall, that half round trim in the corner behind the toilet is the black vent. So there is a bout a 12" section that runs horizontal behind the bath mirror/cabinet that could have been plugged by mud daubers or who knows what? We have Acorn Woodpeckers that will fill vents with acorns if given the chance, a friend had an Oak tree growing in his toilet vent in his lake cabin that plugged the drain eventually.
You could try at your own peril using one of those drain clearing tools from the top that go on the end of a garden hose that first expand to seal in the pipe then shoot a jet of water, leave the black tank drain open while doing so.

On second thought try a shop vac first in case it's something like acorns.

And I just see that it's a 29 and may be much different layout than our 25.

https://www.amazon.com/G-T-Water-Pro...0S4DYCJV3B9XDJ

[Re-Pete]

Originally Posted by AlinCal

I can tell you the vent in my 91 has two 90 degree bends just below the roof were it offsets to get in the corner of the bath wall, that half round trim in the corner behind the toilet is the black vent. So there is a bout a 12" section that runs horizontal behind the bath mirror/cabinet that could have been plugged by mud daubers or who knows what? We have Acorn Woodpeckers that will fill vents with acorns if given the chance, a friend had an Oak tree growing in his toilet vent in his lake cabin that plugged the drain eventually.
You could try at your own peril using one of those drain clearing tools from the top that go on the end of a garden hose that first expand to seal in the pipe then shoot a jet of water, leave the black tank drain open while doing so.

On second thought try a shop vac first in case it's something like acorns.

Looks like I have the same setup. Upon closer inspection, that has to be the case from where it exits the roof close to the bathroom vent fan. I'd already concluded that the rounded trim on the inside corner to the right of the medicine cabinet covered the stack, but I hadn't checked that location against the roof exit until your post, so thanks for that info. The screen that covers the vent pipe would prevent mud daubers or acorns for that matter, so if that is the problem then it's existed for over 7 years.

Doubt I'll try that pressure nozzle, I'd still have to cut the screen and then risk a lot of water damage. The vacuum is a pretty good idea. I have a small wet-dry vac. If the hose will fit I might be able to clear the blockage that way. I'll certainly give that a try.

Thanks again.
Pete

[rmkrum]

Wet/dry vacuum applied to the vent on top before you cut the screen might be worth a try first. Just might pop out the clog, or at least suck some air in there to stir what's clogging it. Try applying the suction for a few seconds, then take the hose away and see if the water is still in there. Worst that could happen is the vacuum would inhale some small amount of stinky water...as long as the black tank is empty

[Re-Pete]

Originally Posted by rmkrum

Wet/dry vacuum applied to the vent on top before you cut the screen might be worth a try first. Just might pop out the clog, or at least suck some air in there to stir what's clogging it. Try applying the suction for a few seconds, then take the hose away and see if the water is still in there. Worst that could happen is the vacuum would inhale some small amount of stinky water...as long as the black tank is empty

Makes sense. not sure it's powerful enough or that I can get a tight enough seal, but I got nothing to loose. [emoji12]

Thanks,
Pete

[A W Warn]

On one of my 1970's trailers I noticed a squirrel dropping acorns into the vent. When I looked the pipe was almost full. Maybe the PO of your trailer installed the new screen and didn't realize there was a blockage.

[Re-Pete]

Originally Posted by A W Warn

On one of my 1970's trailers I noticed a squirrel dropping acorns into the vent. When I looked the pipe was almost full. Maybe the PO of your trailer installed the new screen and didn't realize there was a blockage.

I'm sure that would be the case. The PO who would have done the screen did an excellent job maintaining and improving this Airstream.

[Foiled Again]

Hey Pete! Don't ask how I know this works. Empty and rinse your black tank, fill the toilet bowl qitj water, wrap an OLD wet towel around the wand on your small wet dry vac so that it will plug the drain pipe when inserted. Open the black gate and suck. A dab of VapoRub under the nose can help stifle any gag response. Don't be too persistent, the clog could be beeswax and you'll have to cut the screen to get that one.

Paula

PS: if the toilet drains then you need a new seal there too.