Yes, it is possible that a line with sufficient current flowing in it could pull a dowsing rod around. The trouble is, I strongly suspect the influence of your wrist not staying perfectly plumb to the earth exists a greater force than the magnetic field around most things like telephone wiring (small conductors / small current). The best chance of proving this works would be under high-tension lines, where the field strength is relatively high, and they're not buried in the earth (high attenuation per ft of soil).
But there's nothing I can imagine that would cause static water sitting in a pipe to pull on a dowsing rod. I think that science has been pretty much debunked, but I'll admit I've spent all of 20 seconds researching the subject. I'm no chemist, but I suppose it's (remotely) possible that water flowing in a pipe, high velocity and containing the usual minerals and ions, could create a small magnetic field. But buried in the earth and being very weak if any, again the tilt of your wrist will dominate any weak magnetic field/flux effect on the rods.
Electromagnetics is my field of work, albeit high frequency closed-structure stuff. I had to study free-space propagation for my degrees, but have never worked in the free space / antenna field.