I recently went from one sink to two. The water flows great from the faucet but it drains very slowly. I went with vanities that are open undernieth the sink so I had run the drains inside the wall with separate P traps. I put a T on the existing drain and then used PVC in the wall to run each drain. There is no vent in the wall and I am 99% confident that there is not a clog. Do I have a venting problem? How can I fix it without tearing in to the wall?

Hi Pat,
It sure sounds like a venting problem to me. If you have tied the two traps together with the tee before it enters the wall you can install a AAV, (Air Admittance Valve)(see image) just after the traps and before the drain enters the wall. Otherwise you'll have to open up the wall, reconfigure the fittings and run a vent out the roof. Check out AAVs at http://www.studor.com/
Good luck, Tom

Tom - Thank you very much for your help. Just so were on the same page: The T which connects the 2 drains is in the wall. The P-Traps come off each sink and heads straight in to the wall, no exposed plumbing other than the P traps. If I turn either sink on at a medium flow it takes approx a minute for them to start backing up. Will I need to buy 2 of these AAV's... one for each P trap? I did try to disconnect one of ths sink's P trap's and just have the opening in the wall as the vent to see if that helped the other sink, it did not help. Thank you again - Pat

Hi Pat,

Before you do anything send a snake up into the wall and clean out the drain line. How do you know it's not vented? The vent would be inside the wall out of sight.
"I did try to disconnect one of ths sink's P trap's and just have the opening in the wall as the vent to see if that helped the other sink, it did not help."
Did it suck in air as a vent would or did it back up? How old is your house?
Regards, tom

Thanks Tom. The house was built in 1954. The main drain which is original comes about 3-4" up from the floor inside the wall. Then the T Caps it and it is split 2 ways with PVC to each sink. The T is inside the wall, right between the sinks. The T and everything up from there is brand new, I had the wall open to do the project and finished everything last week. I was considering snaking from the opening in the wall to the T, and then cutting a small hole in the wall to inspect the T and the original drain it is connected to and snake down.
When I remove one P trap so there is an opening in the wall and run the other sink the opening does suck in air... but the running sink backs up. Also, when both traps are connected and I run one sink it backs up after a minute. Then I shut the water off and it drains, during draining sink #2 has water in the trap so I can hear a gurggling noise in its drain.
Lastly, when its draining I hear a slower trickling noise in the wall, not sure if its where the trap meets the wall or at the T.
Again thank you, I appreciate the help - Pat

Hi Pat,
I hope you know you're going to hafta open up the wall and vent the sink. I'm curious, my place was built in 1954 but all the fixtures are vented by code so why isn't yours? Regards, tom

Hi Tom,
My shower, 2nd full bath, kitchen, washer, etc all work great, I am not sure why this one does not. I am thinking that it has to do with going from 1 sink to 2? Or maybe its bad luck. Anyway... I bought 2 of the "cheater valves" like the Studor you showed me to apply to both P Trap's. Will they solve my problem? I tried running both sinks together and they both backed up, but without the other to help with the vent it took forever for them to drain, I think one even stopped until the other fully drained. Anyway - will the valves in the P trap make it right?
Thanks! Pat

Hey Pat,

"I am not sure why this one does not. I am thinking that it has to do with going from 1 sink to 2?"
Both sinks would drain if they were vented properly.

"will the valves in the P trap make it right?"
Installing the AAVs should vent the system so that the vacuum won't be halting the drainage process.
Good luck, Tom

Hi Tom,
Well, the inline vents did not work at all, did not even solve the gargling problem. I was very frustrated so I went to the maintenance department of the company I work for and explained it to them. They said I might have to open the wall, vent, snake, etc... but before I do that I should spend $7 on a gallon of draino... pour it down and let it sit overnight. It worked great! They drain fine and don't gargle. Thanks again for your time and help. Pat

Hey Pat,

A few post ago I recommended snaking out the drain before you went much farther. The lavatories will still have to be vented in any event, that hasn't changed. Glad you're back in business and good luck. Tom