Trying to locate the old line that is buried that supplies water to part of my water sprinkler system. It may be cqopper or PVC.

You will have to find an end to determine metal or plastic.
With Metal, you could use a metal detector.
With plastic, you could push a wire through the pipe and follow with a locator or detector. It may locate a 90, in which case you would have to dig it up and push wire in again.
I have seen, but not be able to find again, is a locator that can locate plastic pipe. I forget if it provides a pulse on an empty pipe, or filled with water?

You can use the wire and metal detector but for 32 bucks you can purchase your very own PVC pipe detector. Check it out at, Armada Tech PRO-1000 - Pipe Finder II for sprinkler and irrigation systems. Good luck, Tom

Tom, I used to think divining rods were a joke until an old timer took a piece of #12 bare solid copper, bent a 90 in it to locate underground wire. I tried it and it worked, it worked well, I asked to keep that piece of wire, he said it was nothing special, still I wanted what I knew what worked for me.
I think Have 2 of the locators you provided a link for, buried somewhere in my house, if it pulls out like an antenna and will fold over 90 degrees for use.
I would try a piece of #12, with about 5 inches for the handle(hold loosley, and stick out maybe 12 inches, to form a 90.
Can't hurt.

I've never seen that done, Let me know how you make out. Good luck, Tom

No, I did try it, and it works.
You won't believe it until YOU can do it.
A little strange.

So tell me what you did and how you did it. Back to you, Tom