Leak detection

What counts as a hidden leak

Any leak you can't see directly: a pinhole in a copper line inside a wall, a joint that has let go under a concrete slab, a cracked service line buried between the meter and the house, a fitting weeping inside a ceiling below an upstairs bathroom. Supply lines are under constant pressure, typically 50 to 80 psi in Orange County neighbourhoods, so even a small opening pushes out a steady stream around the clock.

Drain leaks behave differently. They only leak when something drains, so they show up as stains and smells after showers or laundry rather than a spinning meter. Both are worth tracking down, but they're found with different tools, so tell the plumber which pattern you're seeing.

How a plumber finds it

1. 1

   Meter and pressure checks

   With all fixtures off, the meter tells them whether water is leaving the system at all. A pressure gauge on a hose bib, watched over 10–15 minutes with the main closed, shows how fast pressure bleeds off.

2. 2

   Splitting the system

   Closing the water heater's cold inlet separates hot from cold. Many slab leaks are on the hot side because heat and expansion stress the pipe, so this step alone halves the search.

3. 3

   Thermal imaging

   A hot-water leak warms the slab or wall around it. An infrared camera shows that as a bloom of colour, often tracing the path of the pipe.

4. 4

   Acoustic listening

   Ground microphones and contact sensors amplify the hiss of escaping water. The plumber walks a grid over the suspected run and marks the loudest point.

5. 5

   Tracer gas, when needed

   For quiet leaks or deep lines, the pipe is drained and filled with a harmless hydrogen-nitrogen mix that rises through soil and concrete, where a sniffer picks it up.

What happens after the leak is marked

Detection and repair are separate jobs and are usually priced separately. Once the spot is marked you should get options: open up and repair at that point, bypass the damaged section by running new pipe a different way or, if the pipe is failing in more than one place, talk about repiping.

Ask for each option in writing with a price range before anyone opens a wall or floor. If you plan to file an insurance claim, call your insurer at this stage; most want photos of the locate and the damage before work starts.

Emergency or can it wait?

Shut the main valve and call right away if water is visible and spreading, a ceiling is sagging or dripping, or water is near outlets or the electrical panel. A meter that creeps slowly, a warm spot on the floor, or a bill that's crept up over two cycles is real but rarely a middle-of-the-night emergency. A daytime appointment is usually cheaper.