Start with what you have
Construction dates, tap cards and work orders resolve many lines on paper. Routine work such as meter changes, curb stop repairs and main breaks is a chance to record material as crews see it.
Field observations
Photos at the meter box and where the line enters the building are cheap and fast. Locating the curb stop and meter box first means crews aren't hunting for paved-over boxes.
Sampling and models
Statistical sampling and predictive models help decide where to look. Both need physical verification at real addresses, which is where located and mapped service connections save time.
Verification by excavation
Excavation gives a direct look at the pipe but costs the most per address. Locating the service line and nearby utilities first keeps the hole small, in the right place and clear of other lines.