Hi guys, new guy on the board, im working a pool with flag stone layed over 6" of concrete, the pipe is about 15 " under the concrete. Its a 2" line, i can hear the leak , but can not get a pin point on it because the stone is hollow sounding. I have a 5' section i know its in, just cant put an X on the spot..
'

If you have the equipment you can try these ideas:

1. Hydrophone, with the pump off, insert the mic down the suspect lenth of pipe, often there will be a sudden sound drop after going past the leak and the cable length can be measured
2. If you have a Micro Explorer inspection camera you can inspect the pipe, sometimes the leak is clearly visible, sometimes if you find a suspected fitting you can send dye down the pipe and watch it at each fitting, also if your leaking pipe is a skimmer pipe you can run the filter fully on that line (making enough suction so air is drawn in to the pipe), now insert the camera down the pipe and watch for the air bubbles erupting into the pipe at the leak location, again you can measure the cable lenth to id the spot, or if your camera has sonde capabilities it can be tracked for location and depth
3. Drill holes thru the grout between stones along your path (easy to patch holes after) insert the listening rod setup, or probe each hole for wetness also helps

Welcome to the forum, please report back on your efforts!
Bruce
poolrepairdiver.com

thanks Bruce, i think im gonna try to drill some holes and see what i find.