Dual drainage from double basin kitchen sink? What's the purpose?

Plumbing Forums

Help Support Plumbing Forums:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

ajm513

New Member
Joined
Oct 12, 2021
Messages
3
Reaction score
0
Location
Tampa, FL
Hi all, I searched the forum but couldn't find my specific question. I'm replacing my old double basin kitchen sink with a single basin one. As you can see in the picture, there are currently dual drainage pipes going into the wall. What is the purpose of this is? I've seen dual drainage routed into one and then into the wall, but I haven't seen this before. At first I thought the left drain pipe was a plumbing vent, but it's connected to the sink. I guess my question is, when I replace the sink with a single basin single drain one, which drain pipe would I use and also what would I do with the other drain pipe, cap it?

Sorry for the messy kitchen cabinet. Thanks in advance!


Edit: Some more information that might help. This is a first floor kitchen. There is a dishwasher to the left of the sink and about 5 feet to the left is a washer/dryer stack. Directly above the kitchen sink is a second floor bathroom with a single basin sink and shower. I'm wondering if the sink drain on the left is a wet vent to the drain on the right from the bathroom above. If so, is this up to code currently?
 

Attachments

  • A802F73A-D3EF-40D3-8FEB-8C9F0396EAA2.jpeg
    A802F73A-D3EF-40D3-8FEB-8C9F0396EAA2.jpeg
    2.3 MB · Views: 20
Last edited:
Cap one drain off, you pick which one would be most convenient to use and which to cap off.

You could use a clean out to plug the unused drain.

Kitchens can be piped several ways. It’s just how the plumber decided to pipe it.
 
Thanks for the reply. So you think they're both just draining into the same output?
 
Last question: is there any benefit to leaving it open to use it as a vent? Or do vents always have to exit through the roof?
 
Last question: is there any benefit to leaving it open to use it as a vent? Or do vents always have to exit through the roof?

You can’t leave it open, it would stink.

Yes, vents usually exit through the roof.
 

Latest posts

Back
Top