How to Know Where a Pipe Is Leaking Behind a Wall

Take note of the conditions in which the leak occurs. Leaks on a rainy day may be caused by a hole in the roof. In that case, the leak is not from a pipe.

Listen through the wall to listen to the source of the leaking water. A louder drip may indicate that you are close to the source of the leak while a faint drip may indicate the source is farther away behind the wall.

Run the water in the sink or bathtub that is above the leaking wall. Watch for an increase in the intensity of the wall leak while the water is running. If the leak intensifies, a drain pipe is the most likely cause of the leak.

Cut a small slit into the wall with a utility knife. Cut a small square piece with a drywall saw that will be just large enough to insert your head in the hole. Search for the leak with a flashlight to find the source of the leak.