Confirm water is actually moving
Stop all use — toilets, appliances, irrigation, and treatment-equipment cycles — then record the meter and check it again after waiting. On a private well, watch pressure and pump cycling instead. Then dye-test every toilet (a few drops of food coloring in the tank, wait ~10 minutes, check the bowl for color) before assuming anything more dramatic.
Read the location clues
Ceiling rings, soft drywall, warped flooring, and musty odor suggest a wall or ceiling leak — but note when the moisture appears (constantly vs. only during a shower or flush), which helps separate a supply leak from a drain leak. A warm patch on a slab floor may mean a hot-water line beneath it, though HVAC, sunlight, and appliances can mimic the same pattern. Outdoors, wet or unusually green ground, erosion, or pump cycling with fixtures off can point to a buried service-line leak — soil can absorb a leak without ever producing a visible puddle.
How professionals actually find it
Pressure testing isolates sections; acoustic listening detects escaping water under pressure; moisture meters and thermal imaging add supporting evidence (thermal imaging shows temperature patterns, not X-ray vision). No single tool guarantees an exact location in every structure — a responsible diagnosis narrows the area before opening a wall, floor, or slab, rather than guessing.
Don’t open the wall yourself
Document the moisture, protect the area, and shut off water if needed, but let isolation testing happen before cutting into a surface based only on a stain or a sound. If insurance may be involved, photograph everything, save invoices, and contact your insurer promptly — coverage depends on your specific policy.
Quick answers
Does meter movement always mean a plumbing leak? It means water is being used or lost — rule out toilets, irrigation, and treatment equipment first.
Can a slab leak be found without breaking the floor? Often narrowed non-destructively, though final repair access may still require opening or rerouting.
Can a leak stop and start on its own? Yes — pressure, temperature, and fixture use can make a leak intermittent.