Funny you say that. My parents bought a house 20+ years ago. The original owner had just finished renovating the basement at that time. The water meter was buried behind the drywall with only the readout screen visible and another hole in the drywall for the main shutoff valve.

Fast forward 12-13 years, and they were changing all the old meters out for the digital one they can read from outside your house. The installer comes in to check the old valve before installing it, and had to break away a bit of drywall to pull the old vlave. He sticks his hand in the wall and feels something. breaks the wall open a bit more, and there is a line coming off of the main line before the meter. turns out the line fed the hot water tank. so for the last 13 years they weren't paying for any hot water. Also the installer said the old valve was installed in reverse (water coming into house going through output side of meter). He said that the impeller inside the meter is designed to meter water flow in only one direction, by reversing it the meter only reads about 1/3 of the water going through it.

The bad part, they monitor you water usage for the next 6 months, take the average and back charge you the difference in usage plus interest. I forget how long the went back for but I think it was at least 5 years worth.

Needless to say my parents were not happy campers.