salmonriverhotrock
New member
The septic tank drain field sewer system here is old and finally is in need of replacing the old pipe and drain field. Without any real drawings to go by, it was dig out the 505 time. I was not around when they backhoe dug from a known septic tank out to where the non metallic pipe joined a larger one but we knew from there to however far had to be a collector box where the drain field begins. I fired up the 505, placed it in the all metal mode with no discrimination, full sensitivity, raised the standard concentric coil above the ground about 5 feet and ground balanced it, then slowly lowered it back down to about 2 or so feet until just breaking the audio threshold with headphones on.
After swinging for a ways, I noticed a location about in line with the exposed run that was giving me a slight increase of activity. It seemed to be repeatable no matter what direction I worked into it. I began to make marks with my shoe in the dirt and gravel and it began to form up a visual area about 4 foot by about 8 foot long. When I detected down it's length, the sound swinging in would slightly increase and then around the middle would have a little more increase with some lite crackling and then passing to the other side would go back to that slight increase like the other side and then it would drop. My coil swings were not fast at all. I made sure I could repeat this about 3 times and then told the guys dig here, Sure enough as I suspected, an old iron pipe maybe 6 inch diameter by about 8 foot long running into a concrete collector box for the start of the drain field.
I've used this same technique finding highway culverts though bigger and deeper. This pipe was 3 foot deep plus I ran about 2 foot give or take above ground. Ground balancing at ground level or 2 inches above was useless in trying to hear it. Not until I eliminated physical earth or the ground from the coil could I repeatedly hear the target.
This may not be digging for coins and rings but it could be useful in searches for buried caches or can be used if your ground is a bit too hot or trashed out for coin hunting. I have had some successes with this in trashed areas that I did not have my 4" coil with me. Just keep in mind swinging low to the ground is not your only option and I really doubt there are many who have played with getting earth away from their concentric coils.