DampWatch — hidden leak and moisture ingress in hotel walls

Water changes how WiFi travels through a wall more than almost anything else in a building. A hidden leak makes signals through that wall section slow down and fade — in one spot, a little more each day. Nothing else in a hotel drifts like that, which is why the alarm is trustworthy.

In the physics: Water ingress raises local eps_r from ~2 (dry drywall) toward 80, increasing path delay and attenuation for every ray transiting that wall section; the change is spatially localized and monotonic over days — a signature nothing else in a hotel produces.