A pressurized fitting or pipe leaks during use and wets hidden layers before a ceiling or wall stain becomes visible.
Failure path
- Step 1: Water pressure is present.
- Step 2: A fitting releases water behind the finish.
- Step 3: Cavity materials absorb and redistribute it.
- Step 4: The stain changes after shower use.
- Step 5: Drying slows if finishes trap moisture.
What makes this pathway plausible
The timing, location and operating or weather trigger should repeat. A diagram shows a mechanism; evidence from the actual house determines whether it applies.
Best next observation
Record the trigger and compare the nearest materials, components and routes before opening finishes or choosing a repair.
Verification after repair
Recreate the original trigger when safe, then confirm the symptom does not return and affected materials are stable or drying.
Trigger→Pathway→Symptom→Verification
Simulation boundaryThis pathway explains a plausible mechanism. It does not establish that the mechanism is active in a specific house without matching evidence.
