How a Moisture Meter Solved the Mystery of an Overnight Ceiling Leak

Rude Awakening
One morning I walked into our family room to discover a massive leak in the ceiling. Water had built up behind the overhead paint, creating liquid-filled balloons that bulged threateningly downward. 

Somehow, this had happened since the previous evening, but I had no idea where the water had come from. There had been no rain overnight so I eliminated that possibility. 

Mysterious Source
Next, I turned my attention to a bathroom located directly overhead on the second floor. I was certain I’d find the source of the problem there. I plugged the shower drain and allowed the shower pan to fill with water, then flooded the floor to simulate my kids emerging from their evening baths dripping wet. Try as I might I could not reproduce the ceiling leak.

Tool for Water Detectives
Totally baffled, I decided to use a moisture detector and do some detective work. This inexpensive instrument ($29.98), from General Tools and Instruments, uses two small protruding pins to detect and measure moisture in walls, ceilings and other surfaces. 

By checking the amount of wetness at various points, I was able to trace the leak back to one edge of the family room ceiling. From there, I picked up the trail on the second floor where the moisture meter detected dampness in the carpet and wall of a bedroom closet.

Solved, at Last
The culprit, it turned out, was an obscure backflow prevention valve mounted inside the closet that had malfunctioned at one point, but was now bone dry. Without the moisture meter, I doubt I could have pinpointed the source of the trouble and, ultimately, somewhere down the road, the flood would probably have happened all over again.

Click here for more information on the moisture meter from General Tools & Instruments.