#1 if the leak is outside slab your way is as good as any ! !
But big big But if under slab that water could travel for many feet before you see it and any bubbles rising !
#2 if water is any way coming up into the house where it can cause property damage then he should let HO's insurance in on it
they will pay a leak locate co. To locate leak and pinpoint it for you and give you a better ideal how to bid repair !
And or reroute water pipe overhead to avoid slab