DIY:Water Leak Detection and Pump Cut-Off

Ever worry that if your water pipes leaked or broke, that your electric water pump would fill the basement with well water? An alarm is no good if you're not home to hear it. A sump pump would mitigate, maybe, but it could only compete with the water pump. I wanted a water detector that would automatically cut-off power to the pump.

Having no luck finding a product that does this, I assembled one from available parts. I stumbled across one website where do-it-yourselfers made some excellent suggestions. Unfortunately, one product they recommended had been discontinued in favor of an overly-complex home automation system (X-10). I wanted a simple system: just a highly reliable detector and relay. These components seemed to be the best available.

• Parts:

1. Detector: Winland “Water Bug 200” (WNWB200) with relay output, 1 remote sensor probe included, plus DXAdapter500 mA for powering detector, ~$70 from Absolute Automation.
2. Relay: Opto 22 “120D25” (120V, DC controlled, 25 amp capacity), ~$25 from Allied Electronics (authorized dealer; it is cheaper on Ebay but why risk a defective or counterfeit part to save a few bucks?) This is a solid state relay (SSR), no moving parts and very reliable. I would recommend buying the cover because by covering the contacts it will make the installation safer. My pump is on a 15 amp circuit, so 25 amps is over spec.

• Connections: (see figure). "NC" on the Waterbug means "normally closed", i.e., a closed circuit, under normal, non-alarm conditions. The detector must be powered to allow the relay to close and power the water pump, so in that respect the system is 'fail safe'.
  

• Testing: As the water pump was operating, I placed the water sensor on top of a dampened paper towel. The water pump stopped instantly with no sound from the relay. When the sensor was removed from the damp towel, the pump restarted. I think this shows the system works. However, you are entirely on your own applying these observations, I make no guarantees of any kind.
  

Please post any comments or questions. Good luck!
Note: I recommend the cover, which snaps on an protects the contacts, and the matching heat sink from Opto22. The heat sink protects the relay when the pump runs for extended periods, such as when you are taking a shower or watering the lawn. The cover is cheap. The heat sink is about $35, so about $10 more than the SSR. (added April 17,2011).