Water Leak in a Wall

• A pinhole or fitting failure on a supply line inside the cavity
• A shower or tub valve body leaking behind the wall
• A washing machine supply box or its connections
• A refrigerator or ice maker line run through the wall
• A drain or vent line leaking only during use
• Exterior water intrusion at a window, penetration or stucco crack

Establish whether the wetting is continuous or use-dependent. Continuous wetting with meter movement points at pressurized supply. Wetting only after a shower, or only after heavy rain, points at a drain or the building envelope.

Feel for temperature: a hot-water leak often makes the drywall noticeably warm. Note the vertical extent of the damage — water enters high and exits low, so the highest wet point is closer to the source than the stain at the floor.

Bubbling paint, soft drywall, swollen baseboard or a musty smell at an outlet, combined with continuous meter movement, is a concealed pressurized leak in all but unusual cases. That combination justifies detection rather than opening the wall to look.

Moisture mapping finds the wettest point, thermal scanning shows the shape of the wet area, and isolating the branch serving that wall proves whether it holds pressure. Access is then cut once, at the located point, in the least conspicuous place that reaches it.