Does a double sink need to be vented???

Old 12-25-07, 05:57 AM
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Does a double sink need to be vented???

My kitchen has a double sink in it now and there is no hookup to the vent stack. I know all plumbing fixtures are required to be hooked up to a vent but it seems that the other sink acts as a vent. I also know if that sink is closed, blocked by dishes or the drain is closed it will not act any longer as a vent. I also have seen in a single sink setup a vent pipe under the sink inside the cabinet with cap of some sorts on it and I have heard that code allows these in homes but only two per house.
I am a pretty good plumber here at home and I know my way with the PVC and copper skills but having a window in the wall above the sink as most homes do presents me with a good challenge of where to put the vent pipe. If I can avoid opening this classic plaster wall that would be nice but if I have to I have no problem doing that either.
So, what is the story, vent or no vent. I prefer and encourage plumbing professionals to reply.

Old 12-25-07, 01:34 PM
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you can use an auto vent mounted under the sink. get a good one, not the small black ones but the larger white ones. i think oatey makes them, not sure though. idealy, you'd run a 1 1/2" plastic vent line up as high as possilbe then jog around the window and penetrate through the roof. this will require getting into the wall or running it exposed on the outside.

if the sinks are otherwise plumbed correctly, they can't really vent eachother. they should both be after either a shared p-trap or their own traps. having one open while the other drains sounds like they share a trap and will help the other one drain but isn't really venting.


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