Local codes vary on use of AAVs. In some areas they are not allowed at all, so it's best to check with your local building code folks. Meanwhile a Google search came up with THIS.

That had a lot of good info, thanks. Yes I'm aware of code limitations, they are permissible here. The hookup of the existing services as they were... Well, I'm not convinced was thought out very well. It's not in the cards to replace everything, so it's a case of making things better. The take away from that article is it has to be located after the P trap, and 4" above... Something. Not sure what that something is.

Jake I think you're right. Actually, as I try to explain the issue, I realize there may be more than 1 problems here. So, I have to start somewhere, so here it is. I've made a rough sketch of the outflow plumbing, with regard to the main floor bathroom, and how that exits the house.

You'll notice 2 main 4" sewage lines in this diagram. The one from the laundry room connects into the the one from the upper bathroom on the top side of the outflow pipe.

To stay on track though, this issue concerns the upper bathroom. Here's what we've noticed here:

- this toilet seems to plug the sewage line very easily, I've had to snake out (from the septic end) 4 times in four years. We do not use this b/r for solids and paper products go into a garbage container. ( I think that the outflow from the house to the septic is both too long and too shallow a grade.

The last time it (the septic line) got plugged, the shower drain would drain for a minute or two, then the water would stop draining and start filling the tub. We have heard from the toilet gurgling. The line hasn't been plugged in a while, but tonight I heard the toilet gurgling again, while I was showering, but the tub water was draining with its normal speed, and not backing up.

One thing to note here, there does not appear to be a vent on any of the bathroom fixtures in this room. I know there is a stack on the roof approximately in the area of this room, and on this side of the house, but there is no evidence of a connection. There is no attic access (dry walled shut). I was thinking that I may need to snake out the vent stack from above. This room is where I first considered an Air Admit valve. I was thinking of placing it after the P-trap under the basin.

This is the first issue I need some guidance with. Thanks

Take a strong flashlight and look down the DWV pipes from the roof. Even consider tying a rope to the end of the flashlight and slowly lowering it.

Things have a tendency to fall down the vent tubes and block, either partially or fully, airflow.

Also, when was the last time your septic system was pumped out. You do need to do some maintenance on a septic system over time. And, there has to be room for it to come in, so to speak.

Dan , I don't have a spotter tonight. but that's a good idea. I might enlist a buddy tomorrow. I was thinking about doing that Sunday , but I had another issue to deal with so that got put off. As for the septic, it was done a couple years ago. We're not a high occupancy house, and I was told the tank was oversize for the house based on local code. Not my first home with septic, so it does get a regular "peek" if you know what I mean.

i ran a snake down the vent stack. i got down about 6' and hit something. i pressed and work the snake against it for a while. when i withdrew the snake the first 2" were wet. i put the snake back down and again hit that obstruction, but after a bit again i got past it. i think i got all the way to the maim sewage pipe.. we haven't noticed anything better or worse since doing that, but could be because only 1 bathroom - mine - is on that end of the house and the plumb there..

Were you able to find out what the obstruction was?

To make sure that the obstruction is gone, you may want to put a hose down it to see if the water flows out and doesn't back up. Either the vent tube, or god forbid, sink, tub or toilet.

Regarding an AAV, I have installed a couple where it was below the water level of the rest of the house. I had no problems, but, it was the only thing on that DWV line.

I intend on running a hose up to the roof this week to do just that. I guess I'm missing something, how would water go anywhere but out the drain?

Opening this post back up, since it has a diagram of what is what...

I've written her before about some the the unique things that are going on in my house with the plumbing. This is s a continuation of that - the vent stack.

Now that the weather is better, trying to clear (what i believe is) the vent stack.

today i ran a fish stick down the stack, and initially it felt like it snagged on something, I tried working it out, but couldn't bring it up. Got some light and peeked down. no obstruction visible, but i did see that the fish stick has made a right turn. i could only go so far.

i asked my daughter to go into the b/r and listen for where it might be. She located it, although it didn't make sense to be there (at first) Once I discovered the right angle, it did come together.

So, i knew i was clear fro the roof down, but I have no way of knowing what's going on beyond that. I had to cut into a wooden bulkhead in the basement to look at the sewer pipe...and after 7 years living here, i think i've located where the vent stack connects. The only issue with that is there is no way to do anything with it. I just know its there.

My toilet bubbles pretty good when you flush it, but today there was a slight swirling to the water. I', thinking I may have slightly dislodged something. When the septic pump in the basement ran the water in the toilet still bubbled (just the clear water, nothing else), so there is still substantial plug in that vent.

I would hazard a guess that the roof porting the vertical piece is between an 6 feet long before turning. maybe another 3 or 4 feet, then from the ceiling to the basement, another 8 feet. I would had thought i may be able to access the vent by cutting open a wall behind my A/V equipment, but now, i'm not so sure. I don't want to be randomly cutting up drywall, some i'm entertaining ideas to try and clear the vent pipe.

Since I really don't have an idea about plumbing etc, would there be any merit at all in trying to use a heavy duty (8Amp) shop vac to either force air into the and down the stack, or place it in vaccuum mode and try and pull back anything that far along.

Oh yeah, i dont have any access to the space between the roof and the ceiling. That would be another large hole I'd have to cut.

Part of me thought i could cut through the vent near where it joins the septic, run s snake up to clear, and then bond it back together. Space is limited without some major disassembly of wood work.

With the extra time off work due to our favorite virus, I'm going to make a full count press to clean that vent.

hoping to get some creative, non-destructive ideas.

Be well

S~

What is your vent stack made of? You have to be very careful cutting into cast iron because its heavy and the pipe above the cut must be supported. If its PVC, its relatively easy to cut out a section, and then splice the cutout piece back in using Fernco hubless connectors.

I had problems with my basement commode and found that the vent was connected directly to the side of the horizontal waste pipe, which was apparently allowed when the house was built. However, over the years waste caught on the edge of the vent connection and it was completely plugged. New code requires the vent connection to be in the upper half of the pipe (out of the waste flow) so that this doesn't happen.

I also have vent pipes that go from the basement to the attic and the 2nd floor to the attic, then connect to each other, and then in the attic they run over and connect to the main stack. This is code-compliant because it keeps all the vent connections above the fixtures. You might have something similar that is hidden behind drywall in the attic.

Bruce

All the plumbing is black plastic pipe..

it's been a real question for some time where that vent came down and joined into the system. My contractor buddy who has been helping me thinks that its too far forward of the fixtures, but that was only a guess - he's no plumber.

I don't think cutting into the pipe is going to solve anything or shed any light on anything...

I have located the vent stack connection. If you refer to the diagram above of the sewage pipe, the vent stack is located almost where the arrowhead is for the 4" Main for upstairs; points to the red line.

The actual vent stack is clear. i have done 3 things since last writing.

- snaked the vent stack

- run a garden hose through the vent

- used a shop vac to first vac then blow through the stack from the roof. We were ready for that inside and water did blow up and out of the toilet when we did that. Flow "may" have improved, slightly.

The 3 fixtures ( Sink/shower/toilet) in this upper bathroom have no venting whatsoever.

Easiest option would be to vent from the shower, but that still connects ahead of the toilet and sink, so doesn't really gain anything to solve the issue at toilet.. It would make sense to make the vent connection (or AAV) at the sink, since the sink is last in line. Only thing I'm not sure of is whether I can get above the P-trap and still stay under the sink. ( I could always lower the p-trap , that's just more work). I'm sure the correct option would be to move the exiting vent line to the sink, but the amount of damage to do that isn't worth it. AAV's are code her, so im not really worried about that. Short of gutting the entire house - which is not even remotely going to be considered) I have to do whats best with what I have. If at some point I decide to open make access to the roof space, I may consider augmenting the vent line.