Plumbing services
Leak detection and repair
How to confirm a hidden leak yourself, how plumbers locate one, what the repair involves, and what belongs in the written scope.
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Written by HyrePlumber Research Desk Primary-source research and fact checking
The short answer
Finding a hidden leak and fixing it are two jobs, and they should be quoted as two. Until the leak is located, nobody knows how much floor, wall or concrete has to be opened. A repair price given before that is a guess, and you pay if it is wrong.
If this is happening now
If water is running where you can see it, close the main shut-off first. It is where the supply enters the house: at the meter, or on a basement, crawlspace or garage wall. If water is near outlets or the panel, stay out of it.
What should you do before anyone comes out?
Everything off, watch the meter, and you have evidence before anyone arrives.
A located leak gets a fixed scope. An unlocated one gets exploratory opening billed by the hour.
Recurring copper pinholes are a repiping conversation.
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How does a hidden leak show itself?
Any one of these can have another explanation. Two or three together point to a leak.
With no change in household use, season or who lives there.
Sometimes felt barefoot first. It suggests a hot-water line under the concrete.
A hiss or trickle when no fixture is in use.
A gradual loss, rather than a sudden one.
On a wall or ceiling, with no fixture directly above it.
Or mold that comes back after cleaning and airing.
Soil by the foundation that stays wet, or a green stripe across the lawn.
In one part of a room.
What gets mistaken for a hidden leak?
Rule these out first. Each has a cheaper answer than opening a wall.
| It could be | How to tell |
|---|---|
| A running toilet | A worn flapper can leak silently. EPA WaterSense: “An old or worn toilet flapper can cause your toilet to flush on its own or silently leak thousands of gallons a year.” Close the valve behind the toilet and rerun the meter test. |
| Irrigation, a pool filler or an outbuilding | Shut each one off in turn and retest. If the meter stops, the house is not the problem. |
| Condensation | Sweating cold pipes or a toilet tank in humid weather wet the surface but do not move the meter. |
| A drain-side leak | It leaks only when a fixture runs, so it will not move the meter with everything off. Run fixtures one at a time and watch. |
| Groundwater | A basement wet after rain, dry otherwise, is a basement water question, not a supply leak. |
How do plumbers locate a hidden leak?
Detection is measurement. Each method narrows the location so the repair opens one small area instead of several large ones.
Everything off, read, wait, read again. It proves there is a leak and shows roughly how fast it is losing water.
A leak on the pressurized supply side behaves differently from one that only shows when a fixture drains. Knowing which halves the search.
Branches are shut off and tested one at a time, which can clear whole sections without opening anything.
Water escaping a pressurized pipe makes a sound. Ground microphones and listening discs find where it is loudest.
A hot-water leak leaves a heat pattern in a slab or wall that a thermal camera can see.
An inert gas mix is put into the drained line and detected where it surfaces. It helps where noise, depth or a tiny leak defeats listening.
A moisture meter maps where the water is, and where it is not.
How should a leak job run?
Notice where the repair price appears. It belongs after the leak is located, not before.
The meter test. You can run it yourself and arrive at the conversation with evidence rather than a suspicion.
Whether water is lost with everything off, or only when something runs. The two lead to different searches.
Branches, irrigation, the water heater and any outbuilding shut off one at a time, retesting after each.
Acoustic, thermal, tracer gas, or a mix. The result is a marked spot and a stated confidence, not a general area.
Now the scope is real: which pipe, where, what gets opened and what gets restored. This is when a repair price means something.
A spot repair, or abandoning the run and rerouting it where breaking a slab is worse. Under concrete, ask for both prices.
The meter test again with everything off, because a large leak can hide a small one. Keep the location report and photos for your insurer.
What kind of leak is it, and what does that mean?
Where the leak is and what the pipe is made of shape the repair more than the size of the leak does.
| Leak type | What it means for you |
|---|---|
| Slab leak | A supply line under the concrete floor. Break and repair in place, reroute overhead and abandon the section, or reline. Where it is and whether it is the first one decide. |
| Pinhole in copper | Corrosion that worked through the pipe wall. The patch is easy. The cause, such as water chemistry or velocity, acts on the whole system. |
| Inside a wall or ceiling | A joint, a fitting, or a screw driven through a pipe during past work. Access is the expensive half. |
| Fixture or supply hose | Shut-off valves, supply hoses, fill valves and flappers. The easiest to fix and the easiest to overlook. |
| Service line, meter to house | Often the homeowner’s to repair, but the boundary varies. Confirm it with your water utility before agreeing to anything. |
| Drain side | Leaks only when a fixture runs, so the meter will not show it. Found by running fixtures one at a time. |
What belongs in the written leak repair scope?
Once the floor or wall is closed, you cannot see what was done to the pipe. The written scope is your record.
The marked spot, the method used, photos and the stated confidence.
Its material and size, and what the repair joins it to.
Which was chosen, and the price of the other option if it is under a slab.
The size and place of each opening in concrete, wall, ceiling or floor.
Concrete, drywall, paint and flooring put back, or a line saying they are excluded.
Whether your building department requires one, and who pulls it.
A pressure test or meter test after the repair, with the result written down.
How a new find is handled, and at what rate.
What moves the price of leak detection and repair?
Detection and repair are priced on different things. Keeping them apart on the invoice lets you check each one.
| Factor | Why it changes the number |
|---|---|
| Detection as its own line | Ask for it. Some plumbers credit the detection fee against the repair, which is worth asking about. |
| The method needed | Listening on an open line is quicker than tracer gas under a slab by a busy road. |
| Where the leak is | A hose under a sink and a hot line under the middle of a slab are the same finding and very different repairs. |
| Access and restoration | Concrete, walls, ceilings and flooring opened and put back. Restoration can be left out of a plumbing quote entirely, so check. |
| Repair or reroute | Under a slab these are two different jobs. Get both priced. |
| The first pinhole or the fourth | One pinhole is a repair. A run of them turns the question toward repiping. |
| Timing | Water you can see running is worth an after-hours call. A slow loss found on a bill is not. |
HyrePlumber publishes no national average price for this work. Regional labor rates, access, pipe material and permit fees move it far enough that a single figure would mislead.
Handed a repair price before the leak was found? Ask what it is based on.
A price given before locating assumes a location. When the assumption is wrong, the extra opening, hours and restoration arrive as a change order. Ask for locating first, in writing, as its own line.
What to ask before you sign
And is the detection fee credited if I go ahead?
And what happens if the first method is inconclusive?
A marked spot, photos and a confidence level?
And how did you establish that?
Compared with breaking and repairing in place.
Concrete, drywall, paint and flooring, or only the plumbing?
To confirm the loss has stopped.
What to have ready
Everything off, photo of the meter, an hour with no water use, a second photo.
So the jump can be dated. The date can match something you remember.
And whether it closes.
Warm spot, damp patch, sound, smell, and which rooms are unaffected.
Slab, crawlspace or basement, and the age of the plumbing if you know it.
Irrigation, a pool filler or an outbuilding.
Where this goes wrong
An unlocated leak means exploratory opening, billed by the hour with restoration on top. The plumber cannot know the scope yet, which is why locating should be its own paid step.
Whatever caused the first pinhole is acting on the rest of the pipe. Patching the first is reasonable. By the fourth, ask whether the system should be repiped.
Water runs along joists and pipes before it shows. The stain is where it came out, which can be several feet and a room away from the pipe.
The meter test is free and takes an hour. Waiting a month to see if the bill repeats is a month of water paid for, and a month of water in the structure.
A large leak can hide a small one. Rerunning the meter test after the repair catches it while the plumber is still there.
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Questions
How do I run the meter test myself?
What is a slab leak and how serious is it?
Why should detection be quoted separately from repair?
What causes pinhole leaks in copper pipe?
Can a plumber find a leak without breaking anything?
Does a dripping tap really matter?
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HyrePlumber Research Desk
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