Gurgling and sewer odor

last year

Hi all!

We moved into a home about a month ago. We noticed a sewer smell coming from the 1st floor master bathroom when the shower or bath is running. The smell is not there when the water isn’t running. In the basement, there is a full bathroom (sink, bath/shower, and toilet) that is connected into a sump pump ejector. When the basement bath/shower is running or the toilet is flushed causing the sump pump ejector to kick on it causes a gurgling sound in the master bedroom bath drain and the master toilet release a large bubble and the water level will fluctuate. There seems to be an odor in the basement bathroom while it’s running as well. There does not appear to be any back flow of water into these fixtures just air escape. None of the fixtures appear to be draining slowly.

I tried trouble shooting the vents and found every bathroom in the house appears to have its own AAV in the attic with the exception of the basement bathroom that is tied into the master bathroom’s lines. I planned to replace the AAV valve for these lines but from what I can see it appears to be functional. The line turns before entering attic but from what I can see down the line there’s nothing blocking it. Is it worth snaking it from the attic? Any ideas on what else could be going on or trouble shooting ideas?

I have included pictures of the attic vent set up and the basement bathroom sump pump set up for reference.

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Comments (5)

PRO
Minardi
last year
You need real actual real open to the atmosphere plumbing vents. NO AAV. They are the devil.
klem1
last year
If the roof is metal or tile, running vents through it would be a last resort. Metal roofing is very popular here so 99.9% have aav and I haven't heard of problems. Removing the device will tell you pretty quick if it's at fault. If everything works right while device is removed, increasing size of device might resolve it.

If I only had a single guess I would say a horizonal line is slopped wrong direction causing water to stand and block air. Another thing you might try is temporarily disabling check valve in pump line or otherwise allow line to drain back into sump. If that solves it you could set on/off level wider and let line drain back after each cycle.
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chispa
last year
In a previous house we had a sewer odor in the master bathroom and it turned out to be a bad wax ring on the toilet.
Jake The Wonderdog
11 months ago
last modified: 11 months ago
This is a really crappy plumbing job - pun intended.

Here's the issue: AAV's are a one-way valve, they admit air - they do not allow air to escape.

They only work when paired with a properly vented central stack. So, when water moves through a branch drain, the air in front of it gets pushed out the central stack - and then air is admitted through the AAV to prevent the suction from siphoning out the water in the trap.

I suspect that the check valve on the pump isn't functioning, allowing it to drain down and fill with air. When the pump starts up, it moves a large amount of air into the DWV plumbing.

If there's no central stack, or if it's not connected properly or if it's clogged, the air has to go somewhere and so it comes out of the fixtures. Again, the AAV's don't let air escape, they let it in.

Do you have a functioning central stack vent through the roof?
3onthetree
11 months ago
As noted by Jake, this plumbing was not done by a licensed plumber. As you state you only have AAVs, both IPC and UPC (most all U.S. code), neither allow use of AAV's without a main waste/vent stack as Jake explained why.