We came back home after a week of vacation, and noticed noise in one of the walls of the kitchen which sounded like constant running water in the pipe, though all faucets were closed and dry everywhere. Turned off water outside, and the meter was moving still.

Called a leak detection company that had great recent google reviews, and they came out, inspected and said the area under the fridge was reading 100F which indicated a hot water leak from one of the pipes there. They quoted us $6800 to fix. They said they would dig and go in underneath from outside the house. My concern is how do they know the leak is underneath and not in the wall?

We're going to get a second opinion, but wanted to know any advice to look out for, and what the best plan of action would be.