Match the leak to its timing. Water that shows up after rain points to the roof or a roof drain. Water that runs all day, or only when fixtures are used, points to supply or drain piping above. Stop use of suspected fixtures, protect the area, and confirm the source before anyone opens the ceiling.
What does the timing tell you?
Start with when the water appears.
| What you see | Likely direction |
|---|---|
| Drips only during or after rain | Roof, flashing or a roof drain |
| Steady drip day and night | Pressurized supply piping or a failed valve |
| Appears only when fixtures above are used | Drain piping or a fixture connection above |
| Appears when equipment cycles | Equipment drain or condensate line above |
EMC Insurance's roof drainage guide notes that internal roof drains run water from the roof into pipes that go through the building, and that debris can clog drains quickly in a heavy storm. So a ceiling that drips only after rain can still be a plumbing problem, not just a roof problem. Roof drain leaks get their own page.
What can staff check safely?
Stay out of areas with sagging tile, bulging ceilings or water near light fixtures. Electrical decisions belong to an electrician.
From the floor, you can do the water-meter test EPA describes for commercial facilities: when all water uses are off, read the meter, then read it again an hour later. A significant change means water is leaking somewhere. How to run the test is its own walkthrough. If the meter holds still, suspect rain or a drain-side source instead.
Also ask who is above you. In a multi-tenant building the source may be a neighbor's restroom or kitchen, so the property manager needs the call too. Who handles what depends on the lease.
What happens next?
Controlling the water comes first. If you can tell which fixture or zone feeds the leak, close its valve. Otherwise a plumber isolates sections until the leak stops, then opens the ceiling at the suspected spot. Detection scope explains what to ask for when the source is hidden.
Drying matters too. EPA's commercial-building mold guidance sets 24 to 48 hours as the window for responding to water damage before mold growth starts, and says professional help may be needed to dry an area quickly and thoroughly. Wet ceiling tile and insulation should be assessed, not just painted over.