In some areas water meters have methods of connecting external monitoring equipment to determine water usage over time. This is normally done by a switch that pulses after a certain amount of water consumption. This was the case for sfrwmaker. He has a water meter that has an internal reed switch which closes once per revolution of the last metering wheel of his water meter. He has created a Water Meter Cloud Monitoring Interface which uses atmega328p-pu microcontroller and an esp8266 controller. The system sends data over wifi to the Blynk cloud service to allow the data to easily be stored and monitored over time.
“The esp8266 controller is not very power efficient and cannot run on the batteries for long time. And we would like to use it as web server any time, so it must be powered by the external power supply. It is not good idea to connect the water meter directly to the esp8266 controller because usually the water meters are installed in the dark, tiny space without any access to the external power outlet and WiFi access.”