Have you checked for leaks in the mainline?
Is your water meter open all the way?
Have you had any plumbing work done lately?
Is it with the entire system or only one valve?
did the area you are noticing an issue with ever look great?
Is this a one time occurrence, maybe the city is working on water lines?
What kind of Backflow device do you have? Is it open all the way?
Do you have a master valve?
These are some questions I would ask my self if it were my problem.