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I was trying to secure some bookshelves to the wall, and after using a stud finder to confirm it was drywall (and not a stud), I drilled into the drywall. I met some resistance, so, like an idiot, I switched to a wood screw and just drilled into what was there. I removed the screw and noticed that some black plastic was stuck in the threads of the screw; meaning I had likely screwed into a pipe.

The spot I drilled through is right in the center of a very large wall, so I didn't think it would be likely that the builders would place a pipe there. However, the house is 2 stories and there is a bathroom above the wall I drilled through.

There's no water spilling out yet so perhaps it is a drainage pipe?

All that said, am I screwed? What should I do to confirm that I did or did not hit a pipe? What's the best way to go about fixing this?

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  • Why were you trying to AVOID studs when securing bookshelves???
    – Ecnerwal
    Commented Jun 2, 2015 at 12:32
  • Wasn't trying to avoid studs. Since the stud detector didn't find anything, I used a drywall screw. The drywall screw got caught on something, which I thought was a stud, so I grabbed a wood screw and screwed into it like an idiot.
    – rysama
    Commented Jun 2, 2015 at 12:59

2 Answers 2

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You likely hit the DWV (drain waste vent) stack. This is the drain plumbing for the bathroom and is commonly black ABS plastic.

This pipe is typically empty except when waste is moving though it. Depending on the size of hole, you may find small water spots that gradually get larger or notice a sewer gas odor in that room or nearby rooms.

It is not too hard to apply a patch material to the puncture to fix, but you'd need to cut a good size hole in the drywall to access it. The other option would be to enlarge the hole enough to get the tip of a caulking gun in to fill the hole and then patch the drywall.

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  • @ Ben maybe would be a good thing to firstly verify that what he has drilled through is really vent pipe? And I taught that those pipes only go from the ceiling of the highest floor up to the roof? Lower than that sewerage pipes are being used to conduct gases.
    – python starter
    Commented Jun 2, 2015 at 12:02
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    Cut a big enough hole, patch it well. It's almost certainly the DWV stack, and you really don't want that leaking into the wall.
    – Ecnerwal
    Commented Jun 2, 2015 at 12:31
  • @Tester101 take a look again.....both Ben and I were referring to a vent pipe not sewerage pipe...they are parts of the same system but somewhat different.
    – python starter
    Commented Jun 2, 2015 at 13:18
  • And gravity flow, so no pressure, you will patch both in a similar manner, a hoseclamp to hold the patch in place while it cures, sectioned piece of the same material and solvent weld.
    – Fiasco Labs
    Commented Jun 2, 2015 at 15:34
  • Verification is nice and probably best, but not required. DWV stands for Drain Waste Vent - this is the pipe(s) that connects to the sewer main under the street (but some include the line leading to the first entrance into the floor of the basement of the house) . The DWV pipe will travel from the basement through to the roof. Unless there are problems, this line is almost always empty until you flush a toilet or pour water into a sink. In fact, the city sewer main itself will also be mainly empty, but due to the number of homes on one line it is almost always something flowing into them.
    – Ben
    Commented Jun 2, 2015 at 20:36
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If you can get your hands on some blueprints you see from there, also but this is not so accurate method you can try to figure it out where do pipes go by looking them in the basement, other floors, sewerage vertical pipes location etc. Now when it comes to what you have drilled through there are several options. I don't think that it is water or sewerage pipe because if it would have been water you would find out really soon and sewerage is (most likely) too thick to go through drywall, although it is possible. I’m guessing that you will find that out according to smell or you can try to flush some water and look for leakage or listen for the water sound. There are few more options: maybe you have drilled hose for electrical wires (they can be black, and they are PVC) in this case it’s a good thing you didn't get shocked :) .Also one more possibility is that you have drilled through vapor barrier (again it is usually black and looks like PVC).Those are my ideas :)

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    This is so full of misinformation / misconceptions I really had to downvote.
    – Ecnerwal
    Commented Jun 2, 2015 at 12:34
  • @ Ecnerwal down vote is the least of the problem. Can you please provide correct answer or edit my answer. Main goal is to help OP and plus I'm really curios what are misconceptions.
    – python starter
    Commented Jun 2, 2015 at 13:15
  • @pythonstarter DWV does not contain standing water nor water under pressure; water would not leak out immediately. DWV up to 3" is not too large to fit in a standard stud wall, and when larger pipe is needed larger studs, furring, or a double wall can be used to allow for a larger space. Polyethlyene vapor barrier is typically clear, and is soft & weak and will not provide significant resistance to drilling nor be easily confused with PVC pipe.
    – Zhentar
    Commented Jun 2, 2015 at 22:27
  • @Zhentar I agree that vapor barrier is the least likely option, but the once I have worked with are often black, when it comes to resistance,OP could have also "found" some studs of the dry wall.Now I don't know about regulations in your country but 3" is not near enough for DWV...it must be 110mm (around 4") and typical thickness of drywall is around 3" in total (7,5cm) (5cm for the studs and 2*1,25 for the plaster board).Of course you can make drywall thicker but I haven't found any indication of this in the question. Water wouldn't leak but you would hear it when you flush toilet.
    – python starter
    Commented Jun 3, 2015 at 7:55

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