Device to determine location of the water under the house

According to the technician that services my home oil boiler, somewhere under the slab of my den, there is a hot water leek from the pipes that heat the house. Do you have a piece of equipment, reasonable in price, that could detect where the hot water leak is so that I can have it fixed? The den floor is made of slate. The adjacent bathroom has marble tiles.
Thanks for your help.

Hi

The only products capable of detecting heat through that amount of insulating material are thermal imagers, which start at about $6000. Sorry.