I saw plans for a simalar contraption a while back in a farm magizine. It used an electric fence charger to zap mice. Kinda hard to explain with out the drawing, but it was a copper bridge over a pail of water, the bait hung in a small cage of copper mesh, the mouse would walk out onto the bridge (connected to the ground of the fence charger) and when it touched the bait (connected to the HV pulse off the charger) it would cause it to fall into the water and, in theory, drown. I never tried making it. Seemed a little dumb, as mice like to scurry along walls, not climb over buckets of water and they can sorta swim. I suppose you could do it with line voltage (or higher), then the shock might kill the mouse, but it would be awful dangerous. Your idea of PVC pipe sounds better for the fact that you could lay it along the wall or where the mice run, but it won't allow the dead mouse to fall away from the contacts and you will end up with a really icky fried mouse, and you will have to clean the mouse out before you can get another.
We have somthing call a "tin cat" in our farm shop. Its a metal box with 2 one way doors on it. Mice go in, and can't get out. Works great, even with no bait it fills up with mice. It will hold atleast 20 mice at a time, and if you empty if often, it won't smell like rotten mice.