There is a long, thin, rubber-y line wrapped around/connected to the water line pictured below.
Other angle:
The piece in question is loosely hanging via a zip tie on my main water line about shoulder height and can be moved up/down easily.
Yes and I used to have a well at one house I lived in, and they didn't charge me for water or sewer because of what you say here, they didn't have a way to measure it since I wasn't buying water.