Finished basement sink hooked up to two traps and gurgles when draining

[shansen81]

Hi everyone,

I posted a similar thread previously but thought I'd expand on it with a new post.

My wife and I bought a home a few months ago and we discovered that the sink in the finished basement gurgles when it drains (and then makes a dripping sound for a few minutes after).

There's the standard p-trap under the sink which goes into the wall behind the vanity. The pipe then travels 7-8' feet or so, behind two walls, and comes out in an unfinished closet next to the bathroom. Right before the pipe goes into the ground there's another trap.

Below is a video of the sink draining and gurgling along with a couple photos showing the bathroom and the second trap going into the ground.

Could that second trap be the culprit behind the gurgling sound? Perhaps air is getting stuck between the two traps?

Here's the video:
[ame]https://www.youtube.com/watch?v=9IB7Lfjjdz4[/ame]

The trap underneath the sink goes into the wall behind the vanity then elbows and goes behind the wall to the right of the vanity:

Then it comes out in this unfinished closet (the pipe on the left) and there's that second trap right before it goes into the ground:

Thanks!

 

[CT-18]

You cant double trap a fixture can cause vacuum and other issues. Get rid of that last trap. That is probably what is causing your issues.

 

[shansen81]

You cant double trap a fixture can cause vacuum and other issues. Get rid of that last trap. That is probably what is causing your issues.

Thank you! You said "and other issues" - what could some of those other issues be? Is this something we should take care of right away?

 

[Mr_David]

The drain does not appear to be vented. The gurgling is the water seal in the trap siphoning out. install a AAV under sink after the p-trap.

7-8 ft away in exposed section of drain might be to far away.

 

[shansen81]

The drain does not appear to be vented. The gurgling is the water seal in the trap siphoning out. install a AAV under sink after the p-trap.

7-8 ft away in exposed section of drain might be to far away.

Thanks Mr. David. Perhaps I'm dealing with a two-part issue - issue one being the lack of a vent (which would make sense) and issue two being the double trap (which would also make sense).

Can you elaborate on the last comment about the exposed section of the drain possibly being too far away? Too far away for an AAV or too far away to drain properly?

The good news is that the water doesn't appear to escape from the trap and we don't have any sewer type odors coming into the home. We learned about a month or so ago that those fixtures weren't draining into our main septic tank that we knew about.. it turned out that there was a second septic tank on the property that the basement toilet and sink were draining into, as well as the main kitchen sink and dishwasher. The second tank was almost full and had a tree growing in it! We've since abandoned the tank and had a new sewer line installed so that everything drains to our main septic tank which is in great shape. We just need to find a company to come in to crush and backfill the abandoned tank so we can go on with forgetting that we ever had it...

I appreciate your input!

Scott

 

[Mr_David]

Trap arm from trap to vent should be less than 5ft.
You might get away with 7-8 ft .

Not the right picture I was looking for, but
with proper grade/slope of pipe the top of pipe into santee becomes lower than the bottom of the pipe coming out of the p-trap then the vent becomes useless

 

[shansen81]

Trap arm from trap to vent should be less than 5ft.
You might get away with 7-8 ft .

Not the right picture I was looking for, but
with proper grade/slope of pipe the top of pipe into santee becomes lower than the bottom of the pipe coming out of the p-trap then the vent becomes useless

Ahh I imagine you're referring to the 7-8 feet for installing the AAV on the exposed section of piping that comes out behind the wall in our closet.

Here's what we have to work with under the sink. Is there enough room to add an AAV?