Our recently purchased house has 6 drains for the gutters. Only one has a visible outlet down the hill. All of them have a 4" PVC pipe that leads vertically underground at the house perimeter. When I run water in them, they do not drain out of the existing outlet (that one only drains from one of the six gutter pipes) and there is no evidence of where the water goes (I am guessing underground somewhere. House is on a hilltop and is near Granbury, TX on sandy and rocky soil. My question: Is there a way to identify the location of the drain pipes and/or at least the direction they run? I know I could dig them up, but that seems way too labor intensive. I am not aware of any sensors, etc; but hope something might be around. Thanks.