We had a burst pipe which we thought had burst in the concrete slab of our house. We called 1300 Burst Pipe Locators and the plumber arrived within an hour of our call, he dug a hole near the house wall and used his special apparatus to find the burst pipe, which fortunately was just outside the slab. The pipe was repaired there and then.
The charge for this service was reasonable and we couldn't have asked for better service, would recommend them anytime.