How to Build a Water Leak Detector

by Christopher Donahue

Water leaks can be a nuisance around a home, but they can be life-threatening in many industrial or shop settings. Having a leak detector with an audible alarm provides a degree of protection for equipment and personnel. It is important that the leak detector be sized to alarm when more than just dew or trace amounts of water are detected. If the alarm trips too often, when safe amounts of water are present, the alarm will be ignored or disconnected.

Drill two holes in the insulated pan 1/4 inch apart and at a level from the bottom of the catch pan that will match the amount of water where you want to be alerted.

Cut two lengths of insulated wire to run from the point where you wish to place the leak detector to the place where you wish to mount the audible alarm and power supply.

Strip 1/2 inch of insulation from the end of one of the wires and slip that bared portion through one of the holes drilled in the insulated pan. Repeat for the second wire and second hole, and epoxy the wires into place to seal and secure them. Be certain the bared wire ends are at the same level as the holes, are parallel and are not covered with epoxy.

Strip and attach the other end of one of the wires to the positive output of the power supply. Strip and attach the other end of the second wire to the positive side of the audible alarm. Connect the ground of the power supply to the ground of the audible alarm.

Test your alarm system by pouring water into the catch pan to the alarm level or by using a piece of metal to short the electrodes in the catch pan. Water in the pan will act as a switch to start the audible alarm and alert anyone nearby to the presence of water at the protected location.


  • check For industrial plants, the alarm can be tied into a SCADA system or some other form of remote monitoring.


  • close This system should be cleaned and tested periodically.

Items you will need

About the Author

Chris Donahue is an electrical engineer living in the Dallas area. He has worked on defense projects, semiconductor process equipment, instrumentation and is currently in water utilities. He earned his Registered Massage Therapist (RMT) standing in Texas in 1999.

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