Detecting Water Before It’s Too Late

[mcu_nerd] is like any engineer, which is why his problem of an occasionally leaky water heater sure looks like a research project with no end in sight. Sure there’s probably a commercial product out there that can be had for half the cost and a few clicks of the mouse, but what’s the point in actually solving the problem?

His log starts with research into detecting low battery voltages. Then it was a quick exploration in designing low-power circuits. When the Flexible PCB contest came along, he realized that there was a chance to design a better electrode, and he ended up winning one of the vouchers; which is where he’s at now.

It’s definitely a work in progress, and if anything it’s just a quick five minute read and an opportunity to commiserate with another wayward soul. We do like his clever use of a tealite candle tin as both the second electrode and case for his water detection circuit. There are also some KiCad files and code.

25 thoughts on “Detecting Water Before It’s Too Late

    1. What if you buy a cheap smart leak sensor, that reports once in a while that it’s still working.. and that can last a few years on a single battery.. and that can also tell you the temperature.. and it’s only a few dollars..

    2. A related concept is used by anti-submarine probes launched by various naval platforms. A good example is the AXBT (Air-launched eXpendable BathyThermograph). A lithium cell in the device has exposed plates and seawater becomes the electrolyte. These batteries pack quite a punch.

  1. occasionally leaky water heater? Sounds like a T&P valve fault or the thermostat is bad and it overheats. When they leak normally it’s time to get a new one, or wait till Noah comes to float a boat.

    1. I had a hot water tank like that once — would leak at random, and in small amounts. Finally got tired of it and replaced the whole thing. When I cut into the tank after removal, I discovered that the inner glass jacket had cracked sometime along the way and there were a bunch of rust pinholes in the steel that occasionally water could get to/through under the right conditions.

  2. A water tank leak detector with supply shut off is required by code where I live.
    The detector is a pcb in a paper bag. I think they just duty cycle a resistance measurement. Maybe some correction for ambient temp… or perhaps a simple cap measurement.
    The shut off is a geared motor with a valve. I know they cycle it every now and again to break free mineral deposits.
    The thing beeps when battery is low. Seems to last about 6-9 months.
    Then as a last gasp thing it shuts off the water and dies.. Then you realy know you need to change batteries !

    There is an upgrade to add IOT status reporting too but I don’t have that.
    I thought about whipping up some code for a feather board or something.. but never did.

    There are a bunch of others/similar out there, but it’s still cool to invent alternatives, maybe you can do better than commercial…

    1. Stump,
      Where do you live that it is a requirement?
      I’m interested because I had a leaker about 10 years ago. I would have appreciated having something shut down the water supply.
      I live in NE US.
      Mark Walter

      1. SW usa.
        There is a plastic tray that catches drips and they evaproate over time but with hard water in this area after 10-15 years tanks tend to split or rupture, then it’s continuous running water… Of course they only rupture when you are out of town on vacation.. :)
        I flush my tank every year or less , my last one lasted 21 years , the drain valve itself started leaking so I replaced the entire tank. (I was on borrowed time). The plumber was suprised at the age of the tank. On the new tank I swapped the plastic flush valve for a brass one, it can stand up to flushing better.
        I changed the cath protection once, probably should do that more often too..

        Some tanks are in garages and often there is a pvc drain pipe to the outside from the tray. (maybe there is code on that for new installations.) In my case the pipe drains into the garage !!#@^&? My other water tank tray has no drain at all… (I guess I should fix both of them … day)
        Some tanks are in the attic , plus these drain pipes get clogged over the years (spiders, mice, ants, mud wasps, xmas decorations – another story…..) and they can only handle some leakage rate… Heard enough ugly stories from friends tank ruptures, new ceilings, carpets, furniture…etc..

        Just sharing observations, I am not a plumber. Intersting it looks like very different situations across parts of the world.

  3. The different regulations around the globe are interesting in themSelves. Here the hot water tank should be sitting in a plastic tray that has a drain. So when the leak occurs the water just runs out without damaging things.

    Though this was not always the case so an older installation could use a leak detector.

  4. I appreciate the idea, but this hot water tank has let the owner know failure is imminent. No new information is required as it’s time to replace this bomb that’s going to go off and flood your basement.

  5. Well I have not heard of HW tank exploding but before flushing it sure makes some loud cracking, banging sounds.

    Anwyay , in case it is of use to anyone…. this is the sense/shutoff system I have

    Legal disclaimer : I am not implying or reccmending any of these units are suitable for your use in any way, just sharing what I have.
    Amazon, home depot and others have them
    You can see the sensor strip.

    Seems like a similar one here..

    Hmm…If I had a basement I might think of using one of these for cold water/house shutoff. If any pipe breaks hot , cold, closed loop heating, grey water irrigation system , pressurized hose to washer/dryer/fridge… whatever…… Shutting off might limit damage a bit.
    or perhaps a NN-IOT flow meter that can detect anomalous use, like fridge running water at 3am…..:)
    Sounds like an arduino or launchpad project..

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