I used a 3/32 drill bit for a pilot hole into my dry wall, directly in between 2 wooden studs that were about 32 inches apart, and about 18 inches from the ceiling (of a 1 story house). I mistakenly thought that there was another stud there because the magnetic stud finder was picking something up there. I immediately hit metal behind the drywall, and when I ran my magnetic stud finder along this line, I realized that almost the entire length of this vertical line was metal. What did I hit, and do I need to open the drywall to see if I caused any damage to anything important?

  • It was a pipe. I'll guess a sewage drain or stack. Dec 5, 2015 at 11:50

3 Answers 3


If the magnetic stud finder is showing response across a good part of the stud cavity then there is probably a metal duct in the wall. This could be a stove hood vent, a dryer vent or a heating duct.

If the magnetic finder is showing just a narrow range near where you drilled the hole then the item in the wall might be a metal pipe such as a sewer vent stack, an iron water pipe or an iron gas pipe. Since the first two examples would be pretty rare to use iron pipe I would put biggest odds on a gas pipe.

There is another possibility that you ran into a metal electrical conduit.

  • Metallic conduit? If it was directly behind the drywall, I'd guess it's a larger diameter pipe, or duct. Smaller pipe would be near the middle of the wall, so you'd be deeper before hitting it.
    – Tester101
    Nov 6, 2015 at 14:49
  • Yikes, should I open the drywall and see if I did any damage?
    – dontmatta
    Nov 6, 2015 at 14:51
  • 2
    @dontmatta - If it were me I would start by making a small round hole just large enough to shine a flashlight through and take a look.
    – Michael Karas
    Nov 6, 2015 at 14:56
  • @Tester101 - I agree with you if things were built to codes and customary practices. But sometimes you run into things you would have never have expected. Brings to memory of me drilling through the drywall in my garage, near the ceiling, to hang some thing and drilled right into a copper water pipe that was passing by the area in the framing. The horizontal pipe was surrounded on its other three sides by framing lumber. That caused quite a flood by the time I got the water turned off.
    – Michael Karas
    Nov 6, 2015 at 15:03
  • 2
    Chrome, or grey? .. I've seen some pretty shiny conduit, but usually not "chromed"...
    – keshlam
    Nov 6, 2015 at 20:07

One possibility not mentioned, there may be wires behind the plate if they were not able to locate them far enough back the plate prevents the wires from being damaged by nails, screws ect,,, the plates are usually galvanized steel if that is the case.


Bought a new house and was hanging TV's and pictures. I use a stud finder and then measure. Found what I thought was another stud and drilled with a new 3/32 cobalt drill bit for a pilot hole. Hit something hard and like a idiot put more pressure on it (STOP)...went thru a 2" gas line. Square on...could not have done a better job with a drill press looking at the thing. Silver lining was after the plumber came and did the repairs the 10 psi pressure test showed 4 small leaks elsewhere and he also found badly kinked SS flex line to stove. So $$$, lesson learned, and the the fire dept knows where my house is.

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