Breaking concrete is noisy, dusty and disruptive, and patching it is only half the job if tile or wood sits on top. That is why leak location is a separate, deliberate step. The goal is to reduce the search from the whole floor to an area small enough to open with confidence, or to decide that rerouting makes the exact spot less important.
Methods vary by plumber and by house, but most combine several of the tools below. No single tool is right every time.
Tools and terms you may hear
- Pressure test
- Isolating a line, pressurizing it and watching a gauge. A falling reading confirms that section leaks.
- Acoustic leak detection
- Sensitive microphones placed on the floor pick up the sound of water escaping from a pressurized pipe.
- Thermal imaging
- An infrared camera shows temperature differences on the floor surface, most useful for hot-water leaks.
- Line tracing
- Locating the path of a pipe under the slab, often with an electronic signal, so listening is done along the right route.
- Tracer gas
- In some cases a safe gas is introduced into a drained line and detected where it escapes through the slab.
- Isolation
- Closing valves or capping lines so each section can be tested on its own.
A typical location visit, in order
- Start
- Questions about what you noticed, the age of the house, past repairs and your meter test results.
- Rule out
- Toilets, faucets, irrigation, water softener and water heater relief valve are checked so they are not mistaken for a slab leak.
- Isolate
- Hot and cold sides are separated and may be pressure tested to confirm which line is leaking.
- Map
- The route of the leaking line under the slab is traced and sometimes marked on the floor.
- Pinpoint
- Listening, thermal imaging or other methods narrow the leak to a spot along that route.
- Report
- You should hear, and ideally receive in writing, where the leak is, how confident the finding is and what the repair options are.
When the spot is hard to pin down
- IfReadings point to a small area with good confidenceThenA spot repair through a small opening is usually discussed.
- IfThe leak is under a cabinet, tub or finished floor you want to keepThenRerouting the line above the floor may avoid opening that spot at all.
- IfReadings are weak or point to more than one areaThenAsk whether a reroute avoids the need to find the exact spot, or whether further testing is worthwhile.
- IfThe leaking section tests outside the houseThenThe work shifts to the service line between the meter and the house rather than the slab.
What to ask about the location result
- Which methods did you use, and did they agree with each other?
- How big an opening would you need, and where exactly?
- Is the leak on the hot or cold side, and was that confirmed by a pressure test?
- If you open the slab and the leak is not right there, what happens next?
- Can I have the findings and a sketch in writing?
Common questions
Is leak location separate from the repair?
Often it is quoted and done as its own step, so you can decide on the repair with the findings in hand. Ask how a given contractor handles it.
Can I locate a slab leak myself?
You can confirm a leak and which side it is on with the meter test. Pinpointing the spot under concrete takes specialized equipment and experience.
Does the water need to be on during location?
Usually the leaking line needs to be pressurized, at least for part of the visit, so plan for short periods with water on.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.