Re: finding under ground pipes
Find yourself a full metal coat hanger. Cut it at one lower corner (the end of the long straight bottom. Make a second cut at the top of the opposite shorter side, just under the hook and twist. Now straighten the bend between the long and short lengths to 90*. You've just made a divening rod.
Turn on the pump so water is flowing through the pipes, then loosely hold the short end of the divening rod in your hand with the long portion outward. Hold your forearm and divening rod parallel to the ground and walk back and forth across the area where the pipes are. When you cross the pipe, the rod should turn in your hand with the directional flow of the water.
Second means would be if you know the builder of the pool, call them and see if they still have the plans on file, which will show the locations of all the plumbing.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!