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Double Sink Setup

I have a double bowl sink in the kitchen. The drainage runs out directy below one tub. I have lived in the house 10 years and have always had slow draining out of the other tub. I have tried several times to clean out the slow drain but to no avail. I have taken the plumbing out under the sink and have found nothing that would slow the drain. I also see nothing that looks like a vent of any kind so I'm guessing the builder did not install one. Which doesn't surprise me, he didn't install shut off valves at any of the sinks in the house either. So when I needed to work on a sink I had to shut the water off to the entire house.

Someone mentioned that installing an air admittance vent would help alleviate the issue so here are my questions:

1. Will installing the Air admittance vent help with the draining of the second tub?
2. Where should the vent itself be installed?

I appreciate any help/guidance you guys/gals can provide.


Re: Double Sink Setup

If you ruled out blockages in the slow drain, and since you are positive that there's no vent, go ahead and install one. Look up on the roof in the area above the kitchen to verify that there is no vent. In my city, venting up thru the roof is code, for kitchen and baths.

To install a vent, you need to open the wall between two studs and cut the roof (sorry about that).

I find it peculiar that the builder/plumber did not install shut off valves (angle stops) under the sink. In my city it's also code. If you don't have any, install them - you'll be glad you did.

BTW, how are your faucets connected to the water pipes under the sinks?

Re: Double Sink Setup

I installed the shutoff valves a long time ago, makes things much easier when working on the sink.

Nope, no vent running out to the roof and no sign of any vent running off the plumbing under the sink.

MLB Construction
Re: Double Sink Setup

something doesn't sound right to me. there has to be a vent somewhere in the house for your plumbing system. it might not be through the roof above where the sink is, it could be somewhere else. you wouldn't be able to see the vent, it's all hidden in the wall behind the sink. maybe the pitch of the drain is inverted where it crosses under the sink to go to the trap. i think you would benefit greatly by having a good plumber check out the situation. maybe he can assess the issue correctly and fix it properly before you try doing something you're not sure of and paying more than expected when a plumber has to fix it after you do it.

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