Private eye pi is a Raspberry Pi projects website that deals in programming and electronics of building home security. In one of their post, they have explained the process of building a flood or water presence sensor in your house, if you experience water leak in your area on frequent basis causing expensive damages. This sensor is connected to your Private EyePi alarm system which can trigger the alarm or send email alerts. It provides a dual opportunity where one can wire the sensor directly to the Raspberry Pi or to wireless water sensor.
Water Presence Sensor Status on the Dashboard (Image Courtesy: pivateeyepi.com)
The sensor is designed with pleated strips of metal which change as soon as it detects the presence of liquid and consequently changes the resistance for activating the internal switch. It is mounted at some height with the attached wire along with the wireless sensor or Raspberry Pi. The liquid is made to drain away from the probe and after that, the resistance drop and the switch contacts is brought to normalcy. In case, the viscosity of the liquid is poor, then it might not drain away from the probes. This is not an issue but requires a check as in such situation, the switch contacts remain closed.
As explained earlier, two options are available for building water sensor, one is from connecting sensor wires to a raspberry pi and other is a wireless sensor that communicates to raspberry pi over the radio. The former one requires equipment like Water sensor, Breadboard, or PCB and solder, and a jumper wire, Raspberry Pi and all associated peripherals and resistor while the later includes Wireless Water Sensor, Wireless base station and Raspberry Pi and all associated peripherals.
The sensor can be made for different rooms like for kitchen, front door, basement etc. Both the sets have a different mode of construction and it is available in the details along with the video and prescribed links on their website.
Check out the following website for more details.