The easiest way to tell whether a leak is coming from the roof or the plumbing is to look at the timing. Leaks that appear only during or after rain usually come from the roof, while leaks that show up in dry weather or after using a fixture usually come from the plumbing.
Clues It Is the Roof
- The leak shows up during or soon after rain or snowmelt
- Stains are on top-floor ceilings or near exterior walls
- The spot is near a chimney, skylight, or roof vent
- The stain grows in wet weather and dries out between storms
Clues It Is the Plumbing
- The leak appears whether it rains or not
- The stain is under a bathroom, kitchen, or laundry area
- Water shows up after a shower, flush, or the dishwasher runs
- Your water meter moves when no water is being used
- Your water bill has gone up without explanation
A Simple Test
On a dry day, use the fixtures above the stain one at a time. Run the shower for several minutes, flush the toilet, or fill and drain the tub. Check the stain afterward. If it gets wetter, the plumbing is likely the source. You can also do a meter test with all water turned off to check for a supply leak.
When It Is Hard to Tell
Some leaks have more than one cause. A roof vent pipe that passes through the roof can leak during storms, and a drain line near it can leak too. Water can also travel along pipes or beams before dripping, so the stain may not be right under the source.
Note the date, weather, and what fixtures were used each time you see new water.
If the clues point to plumbing, pinpointing the leaking pipe helps you avoid opening the wrong ceiling. For help sorting out a confusing stain, you can have a plumber walk through it with you at (833) 603-1840.