IF it works, and I have seen many cases where it did not, it requires that you be a "believer". I was on one job where they were looking for a sewer line and dug everywhere the witcher said to. By the time they called me and I showed them where it was, the property looked like a Beirut war zone. (The witcher said "But, there WAS something there" at all the empty holes)Other times it was concrete floors when looking for a water line. I am not a "believer", so it does not work for me, or on my jobs, so I rely on technology to find my pipes. If you want to go "high tech" with your witching, I assume they still make the "ball bearing" shaft witching tool to eliminate the friction of your hand. (REAL high tech would be to have it gyroscope balanced so the shaft always stays vertical and could only rotate when it was over the pipe, but then I doubt that it would EVER find anything)