It's kind of hard to frame the question so I will give the background on what's going on. It seems that one of the companies we work along with at times who build athletic fields had an issue with one of their jobs. They had a contract to go in and raise the baseball field to make it level and smooth. Another irrigation company in the area who had previously installed the system that was there many moons ago was to go out and mark the heads prior to bringing in dirt for the new field. Unfortunately, they did not mark them very well and so there are a lot of heads buried under 18" of dirt. From personal experience, I can take years for a leak to occur from the heads in order to locate them and bring up to proper level. So, I've been given the task since I've been creative to figure out a way we can trace the pipe and locate the heads. One idea was to cut the pipe after the valve and run a fish line through. It may not locate the heads, but at least we have an idea where the line runs. How about is there any thing out there that we can put in water that's metalic and put our inductive coupler on our wire locator around the pvc and be able to trace that? Is that worth trying? Anyways, I'm just trying to figure out creative ideas where the work would cost less to locate these heads rather than install a whole new system.