No obvious source
A hidden leak is a source problem, not a waiting problem.
Occupants often hear water in a wall, notice a warm floor, or get a high water bill before anything drips. Those signals are enough to start an investigation plan.
Collect the signals you already have.
Time of day, hot versus cold, meter movement with all fixtures off, and any room that smells musty. Do not open walls to ‘have a look’.
Least-disruptive methods first.
Thermal, acoustic, and moisture work can narrow a search before anyone cuts drywall. The method depends on the building and the signal, not on a favourite tool.
A hidden leak can still be urgent.
No visible drip does not mean the cavity is dry. If a ceiling is soft or an electrical box is involved, treat it as active and call.
Questions people ask
Can a high bill be a leak?
It can be. It can also be a meter, a fixture that runs, or irrigation. Investigation should not start from the bill alone.
Will you find it without opening anything?
Sometimes the source can be named with non-destructive methods. Sometimes access is still required. A honest finding says which.