Feet Not Rods and Dowsing for What?

My neighbours are building an extension and two unexpected pipe routes have appeared heading under our boundary fence line when digging foundations. I can see the line they follow into our garden and experimented with the rods.

Walking up the side passage between the fence and our garage, I experienced rod crosses in line with both; one a ceramic surface water drain at 90 degrees and a mystery line about 1m depth running diagonally.

Feet not Rods

I experienced a straight forward rod cross near the ceramic drain and after passing back and forth concluded that the cross occurred when my feet were over the drain as opposed to the rods themselves.

The deeper line which looks more like an old power cable; looks as if it has a bitumen wrapping.  I experienced crosses but the rods definitely aligned with the line at 45 degrees to the fence line, again when my feet were over the projected line.

If the detection indicator is the feet rather than the rods then this would explain the experiments so far where different people were a metre out from one another if walking across the line from different directions.

Dowsing for What?

This is a good example of  the question, "What does dowsing detect?" One target is a 4" ceramic with residual water in the bottom and the other, deeper down, looks like an old power cable, about 1.5" diameter with bitumen wrapping so probably copper cores.