Re: OT: underground pipe locating
I'll throw in my thoughts about dowsing for cables and pipes. Have been using the technique for about 40 years now.
I use the technique described by Mr. Partridge. Two brass brazing rods with one end bent at a right angle to form small handles. Hold them loosely in your hands and walk slowly keeping the long extended ends parallel directly in front of you and roughly parallel with the ground. If you are reasonably at a right angle to the item underground, the rods will spread apart when you pass over it.
A couple of caveats - you must hold the rod handles so the extended end does not brush over the tops of your index fingers. It has to be friction free. Also, many people will place their thumbs over the top of the horizontal portion. A no-no. Again friction that hinders the movement. Also, movement will occur if you are walking under overhead wires.
I have shown this to engineering colleagues, telephone outside plant people, geologists and others. There was never an instance where I didn't receive a "you're moving the rods" or "I don't believe it." The I would let them try it. It ended up with quite a few believers.
But it is interesting to note that not all people could get a response. That in itself is perplexing. Possibly because they were holding the rods too tight or something else.
I have located underground cables and smaller wires, energized or no. I also can locate (obviously) piping even of the plastic variety. I had one instance where we were getting ready to install a radar site out in the middle of nowhere. It obviously required some excavation and this was in the days when there was no "call before you dig" services. As a fun thought, I had brought my brazing rods so grabbed them and took off across the field where we were going to do the work. About midway the rods parted. No one believed that there was anything out there but, to be safe, I drove a distance each way to check. Lo and behold, the telephone company had buried a trunk cable right through the middle of the adjacent farmers pastures and right through the property we were working at. The giveaway was cable pedestals discovered about a half a mile in each direction of our location. That was a narrow miss.
A friend asked if I could locate their buried septic tank because they wanted to have a pumping company come to clean it out. First step was to locate the piping coming out of the house. Then I walked along the axis of it until the rods spread apart. That was the end of the tank. Then walked from the opposite direction and located the other end. The owner knew the company who built the tank so I called them to determine the location of the cleanouts. From the spots where I marked the ends of the tank, I measured in to the center of the cleanout ports, dug down 4 feet and was directly on center.
Many say that it is disturbances in the earth's magnetic field from the buried object that affects the rods. But I have been a little skeptical about that due to the nature of the material int he rods that I use. I don't think that there is enough strength int he field to induce any eddy currents in the rods to have them possess any magnetic qualities. So I will say that "only the Shadow knows."
So, I guess you will never believe it until you try it. Best thing is to find someone who does it and learn their technique.
---In TekScopes@..., <telists@...> wrote :
On Sun, Mar 20, 2016 at 3:53 PM, David C. Partridge
<david.partridge@... mailto:david.partridge@...> wrote:
> I use two pieces of brazing wire bent into an L shape - you hold the short pieces in your hand and the long bits stick out ahead of you.
> They will swing as you pass over the pipes. Don't mock it does work to detect underground water pipes.