I recently had a large water leak due to my pool autofill solenoid breaking so I belatedly decided to finish a project that I’d started some years earlier to monitor my home water usage and generate alerts if the flow or usage became excessive.

The system is simple and consists of a water meter with a reed switch pulse counter and a raspberry pi with a piface 2.

The reed switch outputs from the meter are connected directly to the inputs on the piface 2 (the red and white wires on the right hand side). The software I wrote pulsemon can also forward the pulses received over a relay to another monitoring system (the black and white wires) such as an irrigation controller.

The reed relay is just a switch that’s closed magnetically when one of the dials on the meter crosses zero. In the DLJ meter I have the 10 gallon dial is used so there’s a pulse for every 10 gallons. The switching is slow in the sense that once the switch is closed it stays closed for a while until the dial rotates away far enough to for it to be out of range of the magnetic field and to close; this can be on the order of a minute or more for a low flow rate. The pulsemon app is written in go and polls the specified input pin and can mirror that input either to a relay or a CMOS switch output. It’s configured via a json file and can send email when certain flow rate is exceeded as well as a periodic email showing dailing usage. It also writes a timestamp to a log file every thime that it reads a pulse. This can be postprocessed to compare against a monthly bill for example.

I use hypriot as the OS for my pis and deploy this app as a container.