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Looking for under-pan moisture sensor to detect shower leaks

sieler | Posted in General Questions on

redoing our shower (first remodel in 2012 was poorly done, resulting in
leaks).  New shower will use Schluter Kerdi shower system.

But….I’d like to lay down a thin moisture sensor, to detect problems earlier.

Does anyone make one?

I’d expect one design that would work could be merely simple wires that, effectively, measure the electrical resistance of the wood would work … if resistance begins to drop, the wood’s getting wet.

I’d hope for something on the market that doesn’t require
constant equipment connected to it…rather, a jack that you can plug in and
check periodically (and, it wouldn’t require power when not connected).

Cupertino, CA, USA

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  1. Expert Member
    BILL WICHERS | | #1

    I’m not aware of any commercially available systems that would work in this application. There are liquid sensing systems though. I think for a sensor, run two thin (22 gauge or so) stainless steel wires about 1/4-1/2” apart in the area you want to monitor. Put a piece of housewrap (which is vapor permeable) above and below the wires. Put the assembly in the space you’re sensing, which I’m guessing is going to be between the Kerdi membrane and the subfloor in your application.

    The housewrap will protect the wires and provide some limit to erroneous detection due to conductivity of nearby materials (like a nail head in the subfloor), but moisture will penetrate the strips of housewrap to make a current path between the wires. You could use a regular ohm meter to make periodic checks of your system and keep a log to know when things change.

    B and B electronics makes all kinds of industrial monitoring equipment and will likely have devices that can monitor a sensor like I describe.

    There is a very expensive liquid detection system used in datacenter facilities that uses a special cable that looks like a twisted rope. It is used to detect liquid from leaks and the like, and the monitoring system can tell you where along the cable the liquid is. It’s a multi thousand dollar system though, and the cable is about 1/4” diameter so I don’t think it would work in a built-in application. These cable systems are normally laid on top of a concrete slab in a raised floor area (usually 18” or more between the slab and the floor, it’s like a drop ceiling in reverse). I’ve never seen a sensing cable that can be embedded into another material.


  2. sieler | | #2

    Thanks, Bill ... the wire + ohm meter was exactly what I was considering doing!

    I'm just surprised no one is selling a system to do this. Maybe it's like the USB A/B switch ... no one was making one until I asked USB industry leaders about it. So, maybe this is the question that will spur someone :)

    1. Expert Member
      BILL WICHERS | | #3

      No problem.

      The wire is a bit brittle, so I’d bring it out to a terminal strip so that you don’t have to touch the actual stainless wires to make measurements. Using a 2-terminal connector after the terminal strip would make the meter connection easy too. I’d probably just use a TRS type connector.

      Btw, you can use Teflon sleeving (“spaghetti tubing”) to insulate the wires where needed.


  3. Expert Member


    The lower-tech solution I've taken to using on the walls at the drain end of bathtubs and showers is to include a hole and vent cover. If installed before occupancy, the residents don't question its presence, and the access can prove very useful to replace drains or just to monitor the subfloor.

  4. walta100 | | #5

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