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I'm really struggling here with what I think is actually a very simple problem.

I am replacing my sink. I have a black plastic (poly, not PVC) 1.5" p-trap assembly that I wish to keep, because I don't want to replace the pipe running to the sanitary T. I want to connect that to my 1.25" drain, about 6" offset and 6" up.

I do not want to use a flex pipe, and I'm fine with cementing some pipes together. But the trouble is, all I see at stores are white PVC couplings, and I know that PVC and poly are not compatible because they have different wall thickness. I don't see any couplings that I could use to span that distance (while also reducing to 1.25" slip joint, for the drain). I know I could use this to reduce to 1.25", but I don't know how I would attach that to something that connects to my p trap. Can anyone help? Pic:

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Update - additional photo from comments:

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  • A tail-piece extension should get you the added height you need - just screw it onto the existing tail-piece (the vertical part from the sink), then loosen the screw on the trap and swing it around until it lines up. If they don't line up exactly, you can get away with a few degrees of "off". I have...
    – FreeMan
    Jan 8 at 19:29
  • Thanks @FreeMan. I cannot rotate the j-bend into position. it never comes closer than about 2", so I know I need to spend the distance using some coupling pipes.
    – Taylor
    Jan 8 at 19:32

2 Answers 2

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The horizontal arm exiting from the P-trap can telescope in and out of the wall. By moving that in or out, while also swinging the angle of the P-trap, the pair can line up to a drain at any point within about 6 inches of the centerline of the hub on the wall. Sometimes one must extend the arm so that it comes forward beyond the drain tailpiece and the P-trap is swung around to the rear to get the right positioning.

In an extreme situation one might come out of the wall with a straight section, then a slip-joint elbow, then the arm of the P-trap, and adjust the length of the straight section and the arm as well as the rotation angle of the P-trap to achieve alignment.

When the trap is positioned below the tailpiece you can use a tail piece extension, also sometimes called a slip joint extension tube, to bridge the vertical gap. It looks like this: (photo: lowes.com)

slip joint extension tube

If your existing trap's arm is not long enough then you can buy a new one, or you can extend that with a slip joint extension tube as well.

It's fairly standard that the 1-1/2" parts include gaskets to receive both 1-1/2" and 1-1/4". If yours are missing, the gaskets are sometimes offered for sale separately from the tubing parts.

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  • Thank you! I think I'm starting to understand, with the help of you and @FreeMan. I didn't know what was behind that eschutcheon thing, so didn't mess with it, but here's a photo: imgur.com/a/VfI2dW5 So, if I loosen the brass coupling there, I might be able to slide in or out the horizontal arm, and that could help me align the p-trap. Does that brass nut look like an old-style slip joint, to you?
    – Taylor
    Jan 8 at 19:50
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    @Taylor Yes, fully unscrew that nut, clean off the inevitable corrosion/mineral buildup from the horizontal arm, and then the arm should move in and out of the wall fitting. Be prepared for the possibility that the gasket behind that nut will be in poor condition and require replacement.
    – Greg Hill
    Jan 8 at 21:54
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Just look for that chunky compression ring that comes with most trap kits. You'll use it on your drain tail and inside the trap extension running to the trap.

I assume you'll need to buy one since you already have the trap, but they exist. They look just like the standard ones, but thicker.

Example product

Your needs are as follows:

  • An extension to bring the trap forward. This will connect to the wall adapter and the trap arm. It's possible that there's enough pipe to simply slide the trap out, but I doubt it from what I can see.
  • An extension for the tailpiece. This brings the vertical portion down to the trap entrance. This is basically the same thing as above.
  • The washer mentioned above.
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  • Thanks - I think I understand that I need to use the 1.5" to 1.25" o-ring, in order to attach a 1.5" slip joint to the metal drain. But I don't understand what piece (or pieces, since I need to go up and over about 6") I need to attach to the threaded j-bend. I've never seen any couplings or elbows that look like they slip into my existing j-bend.
    – Taylor
    Jan 8 at 19:31

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