Bill, Usually, perticularly inolder places, a plumbing vent pipe is grounded. but if there is any chance of PVC pipe anywhere in the stack, you might get fooled.
It won't hurt anything, just won't perform as well as it might. if you have a handy dandy talking meter, you could test the resistance between any proposed ground and the U ground of an electrical box. Do not, mix up the U ground and any possibly hot socket. or you'll kill the ohm meter. You should get less than a hundrred ohms between any two ground points in the same home. If its higher than that you can suspect plastic or corosion or some such. Basically hook anything metal that's not connected to another electric device up and see if it listens. So long as you stay clear of power lines you can't do any harm. Tom
