Possible Vent Pipe Slippage

[Riverbug]

Wondering if anyone knows how the vent pipes are held in place to prevent them slipping down into the tanks? I have a venting problem with the black tank that started mid-way into our two month trip through Colorado. Now, when the tank is at about 30% (based on our SeeLevel sensors), we will get strong odors only when flushing, and the toilet will begin to burp. It doesn't do either of these things below 30%, but it is very consistent once 30% is reached. That's why I'm thinking the vent pipe has slipped down into the tank. On Thursday (21st) I will be able to go on the roof and pull the vent cover off to see whether the pipe is still above roof level or has slipped down at all. In the meantime I'm just curious why/how it could slip as I assume the pipes are held in place by some means to avoid this sort of thing?

[Riverbug]

Well, in case anyone is interested, I found that the vent pipe has not slipped at all. It is sticking above the roof-line under the vent cap. After putting a scope down the toilet, it appears that the pipe extends below the top of the tank. I couldn't get a great look at it, but it appears to only have about a 2" gap between the bottom of the pipe to the bottom of the tank. I guess that would explain the vent issues at about 30% full. I was not able to move the pipe at all from the roof, so it has been that way from the manufacturer unless something else funky is going on. We realized that the problem didn't begin mid-way through our trip as first assumed, we just didn't have many trips before this one and likely hadn't experienced an issue until we began noticing the odor when flushing. In shorter previous trips we likely didn't fill it very much but weren't paying such close attention until we noticed a problem.

Now to decide if I will tackle the job myself or take it in under warranty. Neither option is appealing.

[sande005]

Mine slipped during our stay this past winter. Same issues you describe. Dealer didn't say why, but it had. Don't know how it was originally fastened, but he pulled it up to a more correct height, put a cross bolt through it so it could never slip again, and gobbed it all up with sealant. Don't know what he had to do on the tank end, but it doesn't leak/smell. Repair labor charge was comparatively cheap, so it must have not been much work. Problem fixed. We now have much more capacity than we did.

[Riverbug]

I was hoping it was a slipped pipe thinking that would be best case scenario, assuming I would be able to grab the end and pull it back up. But ours is firmly in place. We'll be back home in a few weeks so at that point I'll remove the toilet so I can see better into the tank and verify what is going on in there. Not likely anything I can fix without dropping the tank but I'll try to confirm first before I start that process.

[dryfly]

Might be interesting to give Grand Design a call to see how the pipe is attached to the tank before going to too much trouble. If it's "glued" to the tank, then what can you do even if you remove the tank? If not, maybe a little pressure will enable you to lift it up. Cool that you were able to scope it a find the problem!

[Riverbug]

Might be interesting to give Grand Design a call to see how the pipe is attached to the tank before going to too much trouble. If it's "glued" to the tank, then what can you do even if you remove the tank? If not, maybe a little pressure will enable you to lift it up. Cool that you were able to scope it a find the problem!

Not a bad idea. Maybe I could glean more details from them about the setup. Thanks for the idea.

[LMagelitz]

Not a bad idea. Maybe I could glean more details from them about the setup. Thanks for the idea.

I’m pretty sure our vent pipe enters the black tank thru the normal rubber grommet thingy like the gray tanks. If I had this happening, I’d probably cut a section out of the ABS, twist/pull the vent up from the tank, and recouple with a fernco rubber coupling. Then put a hose clamp around the ABS right above the grommet so it can’t slip down into the tank. This is an “assessment over morning coffee” so take it for what it’s worth.

[jh2pizza]

Just tagging along. Ours burps up through the bathroom sink when taking a shower. Was never an issue until we replaced all the supply lines and have volumes of water. Our appears to be glued into place. If so, it’s an easy fix with a Socket saver but for plumbing but it would have been more ideal if the used rubber Uniseal versus glue.

[Riverbug]

Update/resolution: It took some contemplating but I figured out the issue and chose an alternative route to solving it versus the most correct method, which would have been to drop the tank and make lots more work for myself.

The issue: The vent pipe was too long. Whomever installed it appears to have put it together backwards in my view. The top of the vent pipe stuck out of the roof about 1.5", so it sat inside the vent cap just fine. However, the bottom of the pipe was about 2" from the bottom of the black tank. Based on the amount of effort it took to turn and move the pipe, I do not believe it slipped down at all. I believe it was installed that way. Another clue is that you'll see in the photo, there is an adapter glued onto the end of the pipe inside the tank. I believe this is the piece that should have sat on top of the tank so that the end would be through the seal and slightly below the top of the tank. As it is, no amount of force could pull that adapter up through the seal without pulling out the seal itself and requiring the tank to be dropped. Note also how far down into the tank the bottom of the pipe is after pulling the adapter up to the seal. There's no way it make sense to have that adapter on the inside of the tank.

The solution: I pulled the pipe up as far as I could without causing damage to the seal. This required all the force I could muster. I removed the toilet, floor flange and flange seal so that I had as much access as possible into the tank. I then used a 12" drill bit and 90 degree drill to drill holes in the pipe just under the seal at the top of the tank. The drill bit was just long enough to reach. It wasn't a pleasant job but I flushed the tank and used a garden hose with sprayer to spray all sides and top of the tank before I started. I also had to cut 2.25" from the top of the pipe on the roof so that it would fit inside the cap, and I drilled holes in the pipe so I could push a metal dowel through which rests on the roof to hold the pipe just in case it would slip in the future. Following are the pics...

This pic shows how I used a pipe inside the vent pipe so that when I turned and pulled on the vent pipe, it would not collapse.


This pic poorly shows the vent pipe after I pulled it up and inserted the metal dowel to hold it there, although I am not sure it would have slipped anyway. The dowel has a bend on one end so it doesn't appear to be straight through the pipe even though it is. This is also before I cut off 2.25" from the top of the pipe, then reinstalled the vent cap. I also caulked around the pipe itself prior to installing the cap assembly.


This pic shows the vent pipe/adapter inside the tank after I pulled it up as high as I could. The top of the adapter is tight to the seal. I then drilled a hole, went to the roof to turn the pipe slightly, drilled another hole, repeat, repeat, repeat. For some reason this pic posts upside down...


We tested at each step to confirm any improvements. Before starting this project, the toilet would begin burping at 30%. After pulling the pipe up so the adapter was butted up to the seal, it would begin burping at 50%. After all was said and done, I could fill it to 100% (water up to the bottom of the toilet flange) and it did not burp at all.

I hope this is useful for someone out there. At minimum it may help some understand their system a little better.

[smullinax]

Just tagging along. Ours burps up through the bathroom sink when taking a shower. Was never an issue until we replaced all the supply lines and have volumes of water. Our appears to be glued in.

We have the same problem with the shower burping up through the bathroom sink.....but it only does it when the grey tank valve is closed, and the fluid level is 1/3 or more. I haven't dug into it much, but suspect the drain pipe is set too deep into the tank. Roof vent looks OK.