P.S. I don't own a metal detector.

Was the pipe for the filter backwash?

piedmontnc, I don't know how to operate a pool filter.

All, could have mentioned that I suspect that this drain line is tied to ONE drain that is under ONE of my downspouts. Obviously, I'd like to confirm this too. All and all, it would require tracing at least 100' of pipe.

There are other drains for surface water on the property. I believe that they are an older, separate system.

I guess that the only way is to put foot to shovel and start digging? My bunion throbs just thinking about it.

I started back towards this project again this week. I stuck a hose in a clean out near where the pool was that is upstream of where I want to tap in. My aim was to see if the pipe is still clear before I start working. As I waited for a reasonable amount of water to run through it, I thought about how I might tell if the single downspout drain is tied to it.

My pipes then spoke to me. I walked over and listened to the inlet under the downspout and I could hear water running. After I tuned off the hose, the sound stopped. I repeated the process a couple of times so I am convinced that the pool and downspout used the same drain.

Did the hose method work to discovering the run of the pipe? I have buried downspouts that I have no idea where they end - there's no visible exit. They go under a driveway and walkway, so digging is not a good option.

I could tell that two inlets were connected downstream. I did not try to map any pipe runs underground.