Usage and meter clues
An unexplained bill increase and meter movement during a no-use period are two of the clearest reasons to investigate. First rule out household changes, guests, irrigation, running toilets, and appliance cycles.
Changes to walls and floors
Bubbling paint, soft drywall, cabinet swelling, loose flooring, dark grout, and recurring stains can indicate moisture. The visible damage may be some distance from the source because water follows gravity and building materials.
Sound, odor, and pressure
Faint running-water sounds, musty odors, or a sudden pressure change can add context. Each has several possible causes, so the combination and timing matter more than any one symptom.
When to act quickly
Respond promptly when a stain is expanding, water is near electricity, ceilings are sagging, or flooring is lifting. Keep people away from hazards and use the appropriate water shutoff only when it is safe.
This article is general information, not a diagnosis. Keep people away from active water near electricity or unstable materials, and contact 911 for immediate danger.