How do I find a hidden water leak?

Shut off every fixture and watch the water meter. Any movement means water is flowing somewhere on your side of the meter. Then isolate by closing valves section by section.

Last reviewed 2026-07-15

Toilets are the most common hidden loss. A dye test in the tank confirms or clears them in twenty minutes without any tools.

Warm spots on a slab floor, unexplained damp at a wall base, or a water heater that never rests are common indicators of a concealed supply leak.

What to check first

  • Meter movement with all fixtures off
  • Dye test on every toilet
  • Under-sink and appliance connections for damp or mineral crusting
  • Irrigation zones and exterior hose bibs
  • Water heater pan, relief valve discharge and surrounding floor

When to call a professional

  • The meter moves and you cannot isolate the source
  • You suspect a slab or underground supply leak
  • There is staining, sagging or a musty smell suggesting long-term concealed water