I just had a shop sink installed about six feet away from my kitchen sink. The guy who did it insisted it would work but now the kitchen sink does not drain well at all, nor does the shop sink. Here's the setup. The kitchen sink has a trap and then the pipe goes down almost to the floor and then takes a right into the wall. I don't know what's behind the wall. This was the original setup that worked fine. The shop sink was installed another six feet away from the kitchen sink and away from the wall. It drains down through a trap and then has a long pipe that descends only about 8 inches over those six feet and then connects up in a T fitting with the drain from the kitchen sink which I just described. The T is the addition that allowed me to attah the shop sink. I was kind of worried there might be problems here. I think it is some kind of air pressure issue. When the kitchen sink drains it causing bubbling sounds over in the trap of the shop sink; sometimes it will bubble enough and then start draining faster.
Do I need to open up the wall and connect the shop sink directly to the main drain line instead? I don't know about any of this stuff and am worried that I wasted my money on the addition. I can't put the shop sink any closer to the wall because then it's in my kitchen, which defeats the purpose. Please advise.

Hey Stan,

Every fixture that has a trap MUST be vented. I don't see any mention of a vent for the shop sink. If your man didn't installa vent then he left you with a "S" trap which is illegal. What I think happens when you drain the kitchen sink is the discharge goes past the tee which sets up vacuum in the shop sink. As a rule this would be relieved by the shop sinks vent but since the shop sink's unvented it attempts to vent through the shop sinks trap. That's the noise you hear. The vacuum will also slow down the drainage from both fiixtures allowing the chances of a blockage in the drain line. The answer to your problem will be to run a vent on the shop sink. I take it they man who did the installation was not a licensed plumber. I'm sorry but you just learned a expensive lesson. Good luck, Tom

Thanks Tom,
I have a follow-up question too.
I live in a an industrial type building with other tenants and can't put any piping through my ceiling. So I won't be able to put in any new vents that go outside. Would it be all right to put the necessary vent for the shop sink so it just opens up in my room? If so, where should it vent the existing pipe, just somewhere along the pipe before the T joint with the kitchen sink?
It seems to me like this won't work, because then there will be a vent opening into my living space that has direct access to more internal drain lines without a trap in between. So, and bear with my rudimentary knowledge here, it seems to me that the T joint solution is not going to work and I'll need to disconnect the two sinks and have the shop sink go through the wall and connect directly to the main drain line... Then I suppose it can draw on the same vent as the kitchen sink does?
Thanks,
Stan

Hey Stan,

"Would it be alright to put the necessary vent for the shop sink so it just opens up in my room?"

No, if you did that you would be opening a connection from the city sewer into your home allowing sewer gas to enter. Let me give you another option where you don't have to tear up what's already installed. Cut in a vent tee just after the trap, turn the branch up and install a AAV( Air Admittance Vent). A Studor Vent ,(see image) might be just what you're looking for.
Regards, Tom