I recently purchased my house and I am trying to find my internal valve to turn on my external faucet.

Unfortunately the previous owner put in a bathroom in over where the water line enters the house and it also covers the area where the external faucet enters the house.

I'm about to go making holes in the bathroom's drywall and ceiling to find the valve.

I would like some advice for tracing the water pipe so that I may avoid any obvious pitfalls and any advice for when I cut into the drywall for repairing it afterwards. (or maybe I'm going about this the wrong way)

  • Some stud finders can detect wires and other objects in the wall. A metal detector might also work (assuming the pipe is not PEX, or other plastic material).
    – Tester101
    Commented Jun 4, 2012 at 20:28

8 Answers 8


There is no way to trace the water pipe behind the walls with any certainty without using a hole in the wall. If none exists, you will have to make one (plus).

Make shallow cuts in the drywall. A vibrating tool with a circular blade will make nice, clean, sharp, easily patchable holes without cutting so deep as to risk cutting the pipes.

  • 2
    there are ways of tracing pipes depending on the material the pipes are made of, such as location devices that connect to the pipes and send a signal throught them to be picked up
    – UNECS
    Commented Jun 5, 2012 at 2:46
  • Thanks Greebo, hopefully the first hole is close enough to the valve so I can install an access panel on it. Commented Jun 5, 2012 at 17:27
  • 1
    @UNECS None of those will tell you where a valve is located. You still have to cut a hole and look to find that. Commented Jun 6, 2012 at 11:28
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    @theevilgreebo that is true but the question was how to trace water pipes
    – UNECS
    Commented Jun 6, 2012 at 21:24
  • That was half the question: the whole question was how to trace water pipes with the goal of finding the shutoff valve.. Commented Jun 7, 2012 at 12:26

I was lucky and had limited access to the ceiling space that the pipe was running through by opening air ducts and pushing the vents up and out of the way. Using a webcam, a long usb cable and flashlight I managed to scope out the pipe in the space and trace it back to where it joined up to the main water line. Eventually I found the valve through pure chance. It was located inside of a wall stud and underneath a crossbeam rendering it all but invisible.

  • 1
    That's some pretty good detective work there, Biff. Commented Jun 12, 2012 at 14:34

If it's the hot water line, you can find them by running hot water for a few minutes and using an infrared camera. Alternatively, you can use a metal detector like Rizstien said. These options rely on equipment that you may not have, however, so perhaps you'd like to avoid spending $100+.

If you have to rely on cutting into the drywall, make sure you perform what is called a pumpkin cut, explained at 3:00 in this video. This prevents the removed piece of drywall from falling into the wall when you put it back in place and increases its long-term strength. If you cut straight through, it's harder to patch; you have to fasten a piece of wood spanning the gap to avoid these issues and screw / adhere it into place.


If your water pipes are made of metal then you can use simple metal detector to detect route of your pipes. Simple :)

  • 1
    But so is electrical wires, nails, screws, metal studs, gas lines, HVAC ducts, etc.
    – Steven
    Commented Jun 5, 2012 at 15:04
  • pipe will be continues and will have certain path not screws and studs.
    – Rizstien
    Commented Jun 5, 2012 at 15:09
  • Copper isn't magnetic (try sticking a kitchen magnet to a pipe), so some metal detectors may not work. Also, home wiring is continuous.
    – BMitch
    Commented Jun 5, 2012 at 15:20
  • I'd also guess that drywall screws placed 12" apart will look continuous to most metal detectors.
    – gregmac
    Commented Jun 5, 2012 at 15:59
  • And as stated above - you still won't find your valves without actually looking. Commented Jun 6, 2012 at 11:29

Yes, there is a way to view what's behind a wall... There's this new device called DeWalt DCT418 (x-ray) Wall Scanner It can detect through 3 inches and it shows what's actually behind the wall as well. It cost around $300 (at least from Amazon)

I think this would help you a lot.


Check out the Bosch D-TECT 120 Wall and Floor Detection Scanner. This detects things behind walls, but can't tell you what it is. You can also check the D-TECT 150, if you want something more specific.


It occurs to me that an RF wire tracer should also work on metal pipe. Of course if your place is plumbed with plastic that doesn't help you.


There is a device called Walabot DIY, that "sees" through walls and it is relatively cheap. From my experience it works perfectly, many handy mans I used to work with are recommending it.

  • How does it claim to "see"? Is this something that only detects metal?
    – Chenmunka
    Commented Sep 28, 2021 at 17:33

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