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Old 05-28-2012, 04:30 AM   #1
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simple question regarding kitchen sink drain


I am starting the planning of a kitchen remodel and was looking into the kitchen sink drainage. I have a question in regards to the why the existing plumbing was done in the way it was. The sink drain runs through a trap under the sink and then horizontally (the black PVC pipe shown in photo), this pipe connects to a copper pipe and drops below the floor of the kitchen to meet with a bigger vertical drain pipe which runs to the sewer. This connection is not shown in the photos. This vertical pipe appears to change to a smaller diameter and disappears up into the house (could this be a vent?)

Where the PVC pipe meets the copper there is another connection above it from a different copper pipe that appears to go (or come) through the wall and it is not clear what the purpose of this pipe is. People have sworn it is a vent line, but why would this separate vent be required if the pipe which drops below the floor eventually hits a sewer pipe which I assume must be vented (eg, a toilet drain is also connected to this pipe). Could it be a drain for the toilet sink next door perhaps, or some other drain pipe?

The pipes are not optimally located in that they take up cabinet space, and I wondered if anyone had an opinion as to what's going on and/or suggestions as to what to replace them with.

Of course, it not clear, I can clarify perhaps with different photo views


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Old 05-28-2012, 05:05 AM   #2
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A vent needs to be within 5 feet of of the fixture it serves---that's a vent--

the missing picture would help---photo from below--showing the existing run of pipes and the location of the new sink opening--

That existing set up must go in order to install your new cabinets properly.--Mike--


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Old 05-28-2012, 01:30 PM   #3
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Thats a butch job!
Dead ends into a san tee layed on its side with a plug in it,then it runs back to dump into the drain line!
In order for a vent to work right it should be tied in above not below the drain
"facts" have no relevance to this discusion
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Old 05-28-2012, 03:38 PM   #4
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while it not the best looking drain and vent I have seen..thats what it is a drain one is a vent....
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Old 05-30-2012, 10:24 PM   #5
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more info

thanks for the responses. Unfortunately the view from below might not help much. I attached a photo of where the drain from the sink attaches to the bigger pipe and runs to the sewer.

Attached is the kitchen plan which shows the lines. I was hoping to get some ideas on how to improve the situtation. Eg, can I push the vent line to the back of the wall to maximize cabinet space? Can I drop the drain into the floor where the sink will be as opposed to leaving it where it is now where it drops in the middle of a cabinet? Would a mechanical vent make sense, or better to leave the existing setup?

Obviously the vent runs into the wall and it's not clear from below where it goes. One person said it has to run upstairs (2 storey house) and perhaps tie into a vent up there at some sufficient height. I guess that's the confusing part. Why would that be required?

Any suggestions most welcome!
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Old 05-31-2012, 12:52 AM   #6
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I would consider moving the vertical drain into the wall at the right side of the window, put a san tee at whatever height you want the sink's trap arm. Off the top of the tee continue a vent vertical to 42" above the floor then turn it horizontal and tie it back to the exist vent- or run it out through the roof by itself. the side outlet of the tee will continue in the under the window to be stubbed out at the sink.
The drain line should be 2". The trap arm & the vent can be 1.5"
Your existing line looks like 1.5" Too small for todays code. Also, copper tends to wear out with age so check real good. It gets thin like tin foil- wears from inside out
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Old 05-31-2012, 09:32 AM   #7
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Kinda looks like they had to do it that way due to a 6 foot window.

Your new drain needs to be within 3-1/2 feet developed length of where the trap for the sink is going to be.

It looks to me like you might have to run the vent partially through the cabinets before you can get into a wall.

Is there attic space above, or is it a 2nd floor?


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