Basement venting issues

[Homeowner4help]

Hello all, so to start off my house was built ~1920 with an addition some where in the 50’s, and again in the 70’s or so when from what it appears plumbing was added to the house. I’m not even sure if I’m accurate on when plumbing was added, but most every thing in this house was hodgepodged it seems, or so it seems the more I learn. Anyway, today my wife and I noticed on a walk through the kitchen a rancid smell that I’m pretty sure is sewer gas. Especially when the toilet is flushed, shower running, or sink draining (including kitchen sink). It’s been raining the past 16 hours and going to continue for the next 24 it seems according to the weather channel. In the morning I’m going to pop the top of the septic off and see if the level has risen to the level of the pipe? Not sure if I’ll even be able to see that, I’m a mechanic not a plumber. The cover is right out side the kitchen window, and the septic was also pumped like two months ago. Maybe have gotten 2-3 inches of rain now but it’s been slow and every bit of it is going into the ground. Most of what I’m posting for is to know if the vent in the picture attached could be the problem right now or if I just simply need to call a plumber out (not what I want/needed right currently). In the picture the red arrow is the drain pipe coming from the kitchen sink. The green is circling the air dam between the p-trap/drain for the water line off of the water softener deal. And the blue circled is a vent, that I’m curious if that could be venting sewer gas with how much rain we have gotten? The vent is right below the floor in the kitchen where the smell is. Should I be getting a ladder out in daylight and making sure nothing is plugging the vent on the roof for the whole plumbing system? Please advise, not sure what is what and if this can be dealt with with out a plumber!

 

[breplum]

The blue circle is an AAV. They are spring loaded and there is a flat rubber gasket to prevent sewer gasses.
It can be unscrewed from the fitting if needed.
The ptrap could be dry, so check with finger or probe and fill with water and that would eliminate a source of sewer gas.

 

[havasu]

Just curious, but what is the green circle servicing the blue pex line?

 

[Homeowner4help]

Just curious, but what is the green circle servicing the blue pex line?

There is an air brake between the blue pex line is fitted to that 1/2” pvc, the blue pex line comes from the water softener, I assume it’s some degree of a drain for when it cycles?

 

[Homeowner4help]

The blue circle is an AAV. They are spring loaded and there is a flat rubber gasket to prevent sewer gasses.
It can be unscrewed from the fitting if needed.
The ptrap could be dry, so check with finger or probe and fill with water and that would eliminate a source of sewer gas.

I ran the water softener regen cycle to make sure there was water in that p trap.

Will the springs or seal fail in the AAV?

 

[havasu]

OK, that makes sense what the blue pex is doing. With the P trap from the softener filled, is the sewer smell dissipating? If so, you've found the issue. If not, I'd replace the AAV.

 

[Twowaxhack]

I ran the water softener regen cycle to make sure there was water in that p trap.

Will the springs or seal fail in the AAV?

There’s no spring in that AAV. It’s a diaphragm.

The diaphragm is acted upon by pressure to open and close. It’s not mechanical.

If it had a spring it would be considered a mechanical vent. Most codes don’t allow those. We call them cheater vents. It was a first generation air admittance valve.

 

[Homeowner4help]

OK, that makes sense what the blue pex is doing. With the P trap from the softener filled, is the sewer smell dissipating? If so, you've found the issue. If not, I'd replace the AAV.

It did not go away after running the regen cycle. I’ll run to town and get a new AAV today and try it.

I’ve been doing some reading on AAV’s now that you guys said that’s what it is and everything I’ve read said they should be 7-8” higher then flood level of appliance they are acting as a drain valve for as well as being on the floor of the appliance drain. This AAV is in the basement on the kitchen sink drain, probably 5’ lower then the kitchen sink. Should it even be there? If I cap it will the sink not drain well?

 

[breplum]

The kitchen sink above should have its own vent.
The setup with ptrap in a ceiling location is not desirable nor good practice, but was done as a cheap/dirty way to deal with the situation.
It would be too easy to have a clog in the kitchen drain line and have a disaster down there, so changing is a good idea no matter what.

 

[havasu]

Mentioning this is installed in the basement changes things drastically.

 

[Homeowner4help]

I changed the AAV and the smell went away, so it’s fixed on that part of things. But for the rest I’ll call a plumber to come deal with I think!