Water Leak Circuits and Bad Hot Water Tanks

It finally happened to me - my hot water tank blew. As luck would have it, I actually had one of our water leak detection products installed and I was able to get the water shut off within 10 minutes, still had 1/2 inch of water in the furnace room to deal with.

Here is a pic of our wired water leak sensor pcb:

The processor is a PIC18LF14K22, and the circuitry also supports (you guessed it) a temperature sensor, an optional humidity sensor, an audible, and a dipswitch which is used to select a sensitivity.

Here is the actual water leak detection circuit:

The EN_H2O line is driven by the PIC IO line which turns on the 3.3 VDC to the J5 pins for about 1 second. The J5 and J6 pins are stainless steel screws about 1" apart. The V_H2O line goes to an A/D pin on the and the voltage detected easily translates to a reading of water conductivity.

This install saved us thousands of dollars worth of damage if we had not bee notified in time. The rest of the system consists of a wireless gateway and "Enviro Cloud" web based software (see www.vpprocess.com).

Here is a pic of the detector with it's case on:

And here is our wireless version of the water leak detector:

Water leak damage is one of the leading insurance claims and causes billions of damage every year. I was glad I dodged that one :)



1 comment

  • hi,
    useful device. but Q3 in the schematics is not needed in my opinion, as 3V3 from PIC is just as good as from a transistor for such a high-impedance load.

    btw, no transient diode protection used, are you sure the sensor terminals are immune to 500V pulses in both polarities?

    every electronic device sold in EU must comply to that requirement. there are many other requirements of course, but that 8/20 us pulse test described in EN61000-4-5 is the usual destroyer of most of the new IoT devices.

    neeme takis
    tallinn, estonia

    Neeme Takis

Leave a comment

Please note, comments must be approved before they are published