I work as a chief operator in the water industry but also love process control… there are a ton of ways to do this but it all comes down to accuracy for billing… most billing applications are directly read from the meter register via manual read, radio communication, and cellular communication. These will give you the most accurate measurement with the only error coming from the meter… I would shoot for a 0.02% accuracy mag meter… brands such as Krohne, Neptune, Sensus, Badger, Rosemount are big names in the water industry.
Second best option would be to use a meter with pulse output capability using a PLC with a totalizer in the logic. Each pulse represents a known quantity of water.
Worst option would be to totalize a 4-20ma signal. I’ve seen 8% to 20% errors.
There is also a company called SCADAMETRICS (ether meter) that supposedly can take a direct read from a meter and transfer to PLC. This is handy because all the meter manufacturers use different proprietary protocols to read the register directly.
Our systems run as follows Flow meter > PLC > Private Cellular modem Remote> Cellular modem hub >Ignition
This makes for easy deployment for a network of remote devices with one cellular hub.