Need Help: 2 separate drain lines under kitchen sink

Old 07-24-16, 10:40 PM
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Need Help: 2 separate drain lines under kitchen sink

I've plumbed in sinks before many times in homes we've purchased and renovated but I've never seen two separate drain outlets under a kitchen sink before.

There's a metal one down low (see pic attached) and a pvc one up higher. I'm not sure if the previous setup had the garbage disposal draining into it's own pipe? (House was built in 1956)

The lower one appears clogged with debris, while the pvc one is clear but was broken when the kitchen was torn out.

Should I cap one and drain the new sink/disposal into one? If so, should I use the PVC one or the metal one, or does it matter?

I haven't been able to loosen the PVC connection.

Thanks for any help.

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Last edited by PJmax; 07-24-16 at 11:01 PM. Reason: reoriented picture
Old 07-25-16, 06:00 AM
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I would guess that both go into the same pipe behind the wall. The metal one should be capped off. It might be worth cutting out the wallboard and looking at the total picture. Then you can re-fit the pvc piping as you need.
Old 07-25-16, 06:58 AM
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PVC one may be too high to work properly depending on how deep your sink plus disposer will be, so I would check that before choosing. Certainly look like they both go to the same vertical pipe, but as Norm said, removing a little sheetrock for a look see might be in order. You won't have to do a fancy patch job since it will be behind the cabinet....
Old 07-25-16, 07:25 AM
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Is that an outside wall and your in a cold area?
Reason I'm asking is to figure out why those supply lines are coming up out of the floor instead of behind the wall, which is going to make it far harder to install any type of cabinet.
Old steel pipes are always going to be an issue, leaking, rusting and clogging up on the inside as you can see.
Get rid of all of it you can!
Old 07-25-16, 01:16 PM
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I highly recommend you open the wall and cut out the entire old double stacked Tees. They are going to remain a problem if not replaced with ABS or PVC. Your sink will drain much better.

All you need is a new tee, some pipe and two no-hub couplers.

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