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I'm a real novice when it comes to plumbing. I've got a threaded 45 coming out of the wall (white pipe on the right) and an unthreaded black tailpiece coming down from the sink. How do I install a P-trap in this situation?

The new sink is significantly offset from the old one so the angle the 45 is coming out of the wall would be too far forward to meet the drain. I think probably a straight piece and a second 45 would do the trick, but I'm not sure precisely what fittings I should get and how everything should be connected.

under sink close up of drain

Update

I got a P-trap kit along with a longer J piece since I knew the one the kit came with would not be long enough. The problem I have now is that although there is some play in the assembly, there's still no way I can make the connection. I posted a photo below, but I think I first need a tailpiece extension to drop the entire trap down. My first thought about fixing the angle was to replace the 45 screwed on to the stub coming out of the wall with an elbow but I'm not sure there's enough clearance. (Since it may be hard to tell from the photo, cutting back the J piece doesn't solve the problem as the angle is too far off.) Alternate suggestions appreciated.

P trap partially installed

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    Hard to be sure from this picture, but the threaded part from the wall is probably already a slip-joint/trap adapter, not pipe threads. Trap parts are typically different than "normal" plumbing in actual sizes and in using slip/compression joints intended for ease of adjustment and disassembly. Could you edit in a closer picture of the wall fitting?
    – Ecnerwal
    Feb 8 at 12:46
  • @Ecnerwal Done. There was a trap previously installed here so I assume this is indeed already a "trap part." My concern is mostly making sure I get the right part to connect the unthreaded tailpiece to the trap but I'd certainly appreciate advice on the whole setup. Feb 8 at 13:10
  • Yup, that's a trap adapter!
    – Ecnerwal
    Feb 8 at 13:18

2 Answers 2

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Go to your local big-box store (or even better, a locally owned plumbing supply place) and get a standard P-trap kit.

It will include all the pieces you need as well as instructions on how to install it.

There is plenty of adjustment available in a P-trap kit to fit almost any installation situation. You might, possibly need to shorten the tail piece from the sink, but I doubt it.


Looking at your main picture, this caught my eye:

Close up of original picture highlighting possible missing structure

While I get the hack job on the back panel, sometimes that's just necessary, it looks like there may have been a horizontal support rail across here that got removed and these look like the nails/staples that used to hold it on. If that's the case, you may have compromised the lateral integrity of the cabinet by removing it. If your cabinet is screwed to the wall (or another cabinet to the side), it may not matter too much, but if it's free standing, the cabinet could be subject to some racking if there was something removed from here.


Based on the added picture showing the P-trap kit installed but not fitting:

You'll need a tail-piece extension kit to lengthen the tail piece to reach the top of the P-trap itself.

You'll also need another 45° angle or two and a saw to adjust the horizontal piece to get the trap into the correct location.

At this point, your solution is all on you:

  • Take some measurements of what's necessary to get the trap lined up with the sink
  • Stare at the parts at the store, mentally rearranging them until they look like they'll fit.
  • Grab the parts you think you'll need.
    • NOTE: one of these parts you think you'll need is NOT a flexible extension. This will only cause you grief and misery because they'll fit, but they'll clog something fierce.
  • Grab a few extra parts, just in case
  • You might need to use another tail piece extension to extend the horizontal run
  • Fiddle around with all the parts under the sink until you've got an arrangement that'll work.
    • Use tape and a spare pair of hands, if necessary, to hold pieces in place while you fiddle
  • Cut pieces as necessary (the tail piece extension may need to be shortened).
    • If in doubt, cut long. You can always cut shorter, but making it longer involves another trip to the store.
  • Install all pieces, hand tightening the slip nuts
  • Check for leaks
    • Do not turn slip nuts with a wrench more than about 1/8 turn to stop a leak. If you have to turn more than that, something's not right and more tightening won't solve it!
  • Return all the unused parts
    • Alternatively, put them in the "spare plumbing parts to be returned" basket and look at them ever 5 years or so, wondering why you didn't return them right away.
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    I'm not sure what it is that you're looking for, but "the trap itself" is what I think you're after... For example the first item listed at lowes.com in a search for "P-trap" (no endorsement or recommendation). Make sure you get the right size for your plumbing - 1-1/4" or 1-1/2".
    – FreeMan
    Feb 8 at 14:38
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    RE: those staples- they could be left over from shipping. I've had a vanity that had some staples in the back that held some padding material in place.
    – Jamie M
    Feb 8 at 15:30
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    You want a 1 1/2" p-trap. Many of the p-traps work with either size on the sink end, so you just have to get the outlet end correct. For example, the one that FreeMan linked to says "Inlet: 1-1/2-in or 1-1/4-in, Outlet: 1-1/2-in".
    – longneck
    Feb 8 at 18:31
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    @JamieM I had forgotten and wasn't able to check when I commented previously, but there actually is a piece of solid wood stapled to the backside. Feb 9 at 0:06
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    Presuming, @MichaelMior, the "J piece" is the longer horizontal piece, then yes, in general I'd agree with you.
    – FreeMan
    Feb 9 at 17:01
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Below is a picture of what you're looking for. It should be simple enough but pay attention to slope from the trap to the waste pipe connection at the wall. It should be 1/4" drop per foot. You are also going to have to get a threaded compression fitting to connect the crosspiece extension to the waste pipe on the right of your picture. The crosspiece will slide into the waste pipe and you simply tighten the compression nut.
Hint: Assemble the pieces without fully tightening the compression nuts. You might need some play in the assembly. After it's all in place hand tighten the fittings.

enter image description here

Edit: The issue you're facing in matching up the angles is very common when installing a P trap. You're just going to have to go to your local homestore and find the right components to make it work. Below is a pic of a 45 degree elbow that may solve the problem for you.
But it's up to you to do the measuring and decide what may be needed. You might pick up a longer tailpiece dropping down from the sink drain, as well as a few 45s and some straight pieces. The straight pieces are easy to cut and the slip joints are simple to work with. However, we can't determine exactly what will work from pictures. You have to do that on-site. Unused parts can always be returned.
However, stay away from flex accordion type piping. It's notorious for accumulating debris.
enter image description here

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  • Thanks! One thing I didn't realize when I made my initial post is that the unthreaded tailpiece of the sink is 1 1/4", but the threaded trap adapter coming out of the wall is 1 1/2" What is the easiest way to adapt the size? Feb 8 at 17:37
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    When you pick up the compression fitting you'll have the option for a 1 1/4" slip ring. Kits usually contain slip rings for both - but check.
    – HoneyDo
    Feb 8 at 19:46
  • Didn't see your comment before I went to purchase parts, but that's exactly what I found :) Feb 9 at 0:06
  • Turns out the angles are too far off and there's doesn't seem to be enough play to fix with the kit I got. Updated the question. Feb 9 at 0:18
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    @Michael Mior - See additions to my answer in bold.
    – HoneyDo
    Feb 9 at 17:23

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