50's copper radiant system with a leak

Other methods for locating the leaks

I have found and 'excavated' a bunch of leaks in concrete. The IR camera is a good way to go, but a more low-tech approach is to isolate the line, then run soapy water through it with a transfer pump. What I have done is before you run the pump (but have it all set up), get extension chords set up so you can be about where you think the leak is BEFORE you start the pump. Be sure the house is dead quiet. Then, when you are leaning over about where the leak is, connect the plugs of the extension chords together which will start the pump. You should be able to hear a rush of air before the water hits. Once you do, unplug the pump and listen carefully. You should be able to hear it sucking in air. This works quite often. Of course, the other method is compressed air. Sometimes you need a combination of both. But either way, I've been able to very carefully pinpoint leaks with a high degree of accuracy.

For digging out, you can use a SDS rotary hammer drill in the hammer mode to dig out the concrete. Use care and work around where the line is. This is where an IR camera comes in handy, so you don't booger up adhacent lines. I don't use an IR camera, but if you work slowly you can usually excavate w/o daming adjacent lines. But not always, then you've created more work for yourself.