Electric W/H problem - now under slab leak???

Once you determine the location where the pipe enters the slab area, and where it comes out of the slab, draw a line on the slab and drill a few half inch test holes to see if the dirt is dry or muddy. Or if possible, just abandon the pipe under the slab and run a new one

Some Menards sell a cheap moisture meter for measuring wood or concrete moisture content, where it is wettest would be the leak. If it is old copper it might be worth abandoning as acids in concrete have made many radiant heating systems get leaks. A microphone moved along the pipe area might alow you to hear it leaking

Here's a link to message board thread where a problem like yours is discussed:

I would not consider even trying to locate the leak. Just figure out where the pipes enter and exit the slab. Under the slab pipe repairs tend to be very expensive and have to be repeated. The pipe will probably be severely corroded even where not leaking. Save time and money by running a new line above the slab and be done with it.

Don Young