Detection before demolition
The expensive mistake with a hidden leak is opening the wrong wall or breaking the wrong section of floor. Good leak detection works from the general to the specific: first confirm there is a leak, then figure out which system it is on, then locate it closely enough that only a small opening is needed.
In North Orange County homes the usual suspects are under-slab water lines, supply lines inside walls, the yard service line between the meter and the house, irrigation, and fixtures that leak quietly into the drain, such as a toilet flapper. Each one calls for a different test.
Common methods
| Method | What it does | Best for |
|---|---|---|
| Meter test | Watches the meter with all water off to confirm water is being lost | Confirming a leak exists |
| Isolation | Closes valves one section at a time to see when the loss stops | Separating yard, house, hot and cold sides |
| Pressure test | Pressurizes a closed section and watches a gauge for drops | Proving which line is leaking |
| Acoustic listening | Amplified ground microphones pick up the sound of escaping water | Pinpointing leaks under slabs and yards |
| Thermal imaging | Shows temperature differences on floors and walls | Hot water leaks, wet areas behind drywall |
| Moisture meter | Measures dampness in drywall, wood or flooring | Mapping how far water has spread |
| Tracer gas | A safe gas pushed into the line rises through soil and is detected above | Hard-to-hear leaks, some yard lines |
A typical detection visit
- Interview and look.Bills, symptoms, the age of the house and any previous repairs.
- Confirm loss.Meter test with everything off.
- Isolate.Close valves to rule areas in or out.
- Locate.Use acoustic, thermal or other tools to find the spot.
- Mark and report.Mark the location and give a written summary with repair options.
Rule these out yourself first
- Dye test every toilet tank for a leaking flapper
- Check under sinks and behind the washer for wet spots
- Look at the water heater base and the relief valve drain line
- Walk the irrigation system with it running and look for soggy areas
- Check outdoor hose bibs for drips
- Note whether the meter moves with the house shutoff closed
Example: a high bill in a 1960s house
Illustrative example. Not a real job or customer.
A Fullerton homeowner sees the water bill climb two cycles in a row with no change in habits. No water is visible anywhere.
- The meter indicator moves with every fixture off.
- With the house shutoff closed, the meter stops, so the leak is inside the house.
- Toilets pass a dye test. Closing the cold supply to the water heater stops the loss.
- Thermal imaging shows a warm streak across the kitchen floor, and acoustic listening narrows it to a small area.
The homeowner now knows it is a hot water line under the slab and can compare a spot repair with a reroute. This example is illustrative, not a record of a real job.
Common questions
Is leak detection separate from the repair?
Often, yes. Some contractors only detect, others detect and repair. Ask how each part is charged before they start.
Can a leak be in the yard instead of the house?
Yes. If the meter keeps moving with the house shutoff closed, the leak is likely between the meter and the house, or on irrigation.
Will they have to break my floor to find it?
Detection itself is designed to avoid that. The repair may need a small opening unless the line is rerouted.
General information for North Orange County, not a quote or professional advice. In an emergency, call 911.