Gurgling P-Trap

[dgdickens]

Hi Everyone- first time posting:

A while back, my upstairs prep sink began to gurgle every time the sump pump in the basement kicked on. I originally thought that my Air Admittance Valve needed to be replaced, but there was no change to the gurgling after replacement. I finally caved and called a plumber who told me it was a bad AAV and charged me an exorbitant fee to swap a new AAV in for the one I had literally just installed. Still no change. I have drawn a diagram, attached, of the system- it was renovated in 2014 by the previous owner of the house. I had no part in the plumbing choices or layout.

To add to the mystery, I now velieve that, perhaps, it's not a vacuum pulling water from the trap, but air getting blown back up through the line, although I can't think of a reasonable explanation for that. It's just want seems to happen- when the sink has water in it and the pump kicks on, I see bubbles come up rather than the water getting pulled down. Without the AAV, there is no gurgle, but I can't leave the vent open inside the cabinet. And I can't think of a great solution, but it drives me crazy every time the pump kicks on. Perhaps there is someone here who has had a similar problem, or who can think of a clever solution.

I appreciate any insight you can give me

Thanks!
Dan

 

[MicEd69]

Yes, I believe you are correct about the positive pressure being the issue. You don't show dimensions on your sketch, a beautiful one by the way! I think what is happening is your sump pump is flooding the 2" line between its sanitary tee connection to the stack and the wye connection from your prep sink connection to the stack. That slug of water will pressurize the piping below the sanitary tee connection and will result in bubble in your sink.

I don't know how much access you have to the piping, but you could add a "vent" to the 2" line before it connects to the stack and run it above the ppoint where the sump pump enters the stack. That would relieve the pressure when the sump pump kicks on.

 

[MicEd69]

Something like this.

 

[dgdickens]

Something like this.
View attachment 40073

Thank you! This is really helpful. Looks like a pretty straightforward solution. I’ll let you know how it goes, though I may not get to it for a bit- two small boys running around the house make chores like this very challenging!

 

[Twowaxhack]

Hi Everyone- first time posting:

A while back, my upstairs prep sink began to gurgle every time the sump pump in the basement kicked on. I originally thought that my Air Admittance Valve needed to be replaced, but there was no change to the gurgling after replacement. I finally caved and called a plumber who told me it was a bad AAV and charged me an exorbitant fee to swap a new AAV in for the one I had literally just installed. Still no change. I have drawn a diagram, attached, of the system- it was renovated in 2014 by the previous owner of the house. I had no part in the plumbing choices or layout.

To add to the mystery, I now velieve that, perhaps, it's not a vacuum pulling water from the trap, but air getting blown back up through the line, although I can't think of a reasonable explanation for that. It's just want seems to happen- when the sink has water in it and the pump kicks on, I see bubbles come up rather than the water getting pulled down. Without the AAV, there is no gurgle, but I can't leave the vent open inside the cabinet. And I can't think of a great solution, but it drives me crazy every time the pump kicks on. Perhaps there is someone here who has had a similar problem, or who can think of a clever solution.

I appreciate any insight you can give me

Thanks!
Dan

If it worked at one time but recently started to gurgle you could clean the drain.

Thats what happens with cheater vents and combination waste and vents. They can start to act up when the drain gets partially clogged.

Real vents are best.