Not every leak is visible. Water can travel along framing and pipe runs before it appears, so the stain on the ceiling is often nowhere near the actual source.
Unexpected moisture, water stains, reduced water pressure, dripping fixtures, unexplained water use on the bill, damp areas around plumbing, musty smells and visible pipe corrosion are all reasons to have the system looked at before the damage spreads.
Finding the source
Locating a concealed leak means tracing the plumbing, checking moisture levels and testing sections of the system to narrow down where water is escaping. The aim is to open up as little as possible to reach the failure point.
Repairing the leak
Once the source is identified, the repair may be as simple as a fitting or valve, or may involve replacing a run of pipe. Water main and underground leaks are handled differently again, based on where the line sits and how it's accessed.