Generally you can find where the water line leaves the home or well house and usually in a reasonably strait line if done with a chain trencher to the next water fixture.Nothing in this spot but the water lines. I've had the underground utility guys out to mark a couple of times and there is nothing on my property other than what's buried along the road. Once I'm 20' off the roadway I'm wide open other than these water lines and the septic.
If we had known or unknows of their path through the property, we would hand dig until we found it, and that's where we would cross those lines.
A 4" or 5" trenching shovel is a handy tool to keep around.