Plumbing · Service

Leak detection — run the meter test first

Before anyone charges you to find a leak, you can confirm you have one and narrow down where it is. Then decide whether professional detection is worth paying for.

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In short

What is leak detection?

Leak detection locates a water leak you cannot see — under a slab, inside a wall, beneath a yard — without demolishing the building to find it. Professionals use acoustic listening, thermal imaging, pressure isolation and sometimes tracer gas to narrow a leak to a small area before anything is opened. Before you book any of that, run the meter test below: it costs nothing and tells you whether a hidden leak exists at all.

Triggers

Signs you need leak detection

A water bill that has risen with no change in household use
The sound of running water when every fixture in the house is off
A warm patch on the floor, particularly on a slab — close to diagnostic for a hot-water slab leak
Damp, musty smell or mould reappearing in the same place after cleaning
The water meter dial moving with every fixture closed
Pressure that drops overnight with no fixture use
Flooring that lifts, cups or stays cool/damp in one zone
You already fixed a visible drip and the meter still moves

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The job

How leak detection actually works

The meter test — do this yourself, before you pay anyone

Turn off every fixture and water-using appliance, including ice makers and irrigation. Note the meter reading, or watch the low-flow indicator. Wait without using water and check again; any movement means water is leaving the system. That free test is the gate that decides whether detection is even the right booking.

Watch for: A silent toilet flapper. It is the most common cause of a mysteriously rising bill and makes no sound. Put food colouring in each cistern, wait without flushing, and see whether colour reaches the bowl.
Isolate the hot side from the cold side

Closing the cold inlet valve on the water heater and repeating the meter test splits the problem in half. Knowing hot versus cold narrows equipment choice and repair scope before anyone drills a floor.

Watch for: Nobody isolating anything before deploying equipment. The gear is only as good as the area you point it at.
Acoustic detection and thermal imaging

Pressurised water escaping through a small opening makes a noise that carries through pipe and structure; ground microphones trace it to within a foot or two. Thermal imaging maps temperature anomalies that often line up with hot-line leaks under slabs or in walls.

Watch for: Thermal images treated as proof on their own. Sunlight on a wall, a heating duct or a recessed light all produce warm patterns. The image should corroborate acoustic or pressure findings, not replace them.
Pressure testing and tracer gas, for the hard ones

A section of pipework can be isolated and pressure-tested to prove whether it holds. Tracer gas is reserved for stubborn cases where cheaper methods fail — it is powerful and should not be the default first line on every ticket.

Watch for: Tracer gas quoted first. Reaching for it before the cheaper methods inflates the bill without improving the answer.
The report — what you are actually buying

The deliverable is a located leak: a marked position, a depth or wall cavity, an assessment of the pipe involved, and ideally photographs and thermal images. Detection and repair are frequently separate jobs and sometimes separate companies — which is fine when the report is portable.

Watch for: No written location report. A verbal "it's about there" cannot be taken to a second repair quote or to an insurer. Ask what the report includes before booking.

Money

What does leak detection cost?

A professional leak detection appointment is typically priced as a flat fee for the visit, with harder methods such as tracer gas costing more. Repairing the leak is quoted separately and is usually the larger number, especially under a slab. Run the free meter test first.

See the full leak detection cost guide — by material, size and region →

Straight answer

When leak detection is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

You have not run the meter test. It is free and takes twenty minutes. Paying for detection first is paying someone to run it for you.
The dye test showed a leaking toilet flapper. A rising bill with a silent cause is a running toilet far more often than a slab leak.
You can already see the leak. Visible drips under a sink are a repair booking, not a detection one.
Water is actively flooding the house. That is an emergency. Shut the main off and locate it precisely afterwards.
The meter still runs with the house main closed. The leak is on the supply side before the house, and part of that run may be the utility's responsibility depending on your jurisdiction.
You want a whole-house repipe decision, not a pin location. Detection finds a leak; systemic pipe failure is a different conversation after patterns emerge.

Before you sign

What to check when hiring for leak detection

Do you provide a written location report with images?

It is the actual deliverable. Without it you cannot get a competitive repair quote or support a claim.
Is the detection fee flat, or does it vary by method and time on site?

Some firms charge one visit fee; others escalate as methods escalate. Know which before tracer gas gets suggested.
Do you also do the repair, and is the detection fee credited if I use you?

Detection-only specialists are genuinely independent; firms doing both often credit the fee. Both are fine, but the incentives differ.
If you cannot locate it, what do I pay?

Some leaks are not found on the first visit. A stated policy for that outcome marks a serious operator.
Which methods will you start with on my symptom set?

Shows whether they sequence from cheap and informative to specialised, or leap to expensive gear.
Can I take your report to another repair contractor?

Portability is the point of independent detection. Ambiguity here is a red flag.

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Local pros

Leak Detection near you

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FAQ

Leak Detection — questions people ask

Still have a question? Talk to our team →

How do I know if I have a hidden water leak?

Run the meter test. Shut off every fixture and appliance that uses water, then read the meter or watch the low-flow indicator, wait without using water, and read again — any movement means water is escaping. Then rule out toilets with a dye test before you assume a slab.

What are the signs of a slab leak?

A warm patch on the floor is the most telling and points at the hot-water line. Others include running water heard with everything off, damp at the base of walls, flooring that lifts or stays wet, a musty smell that returns after cleaning, and falling pressure. Confirmation still needs methodical isolation — warmth alone can mislead.

Is leak detection really non-destructive?

The detection itself normally is. Acoustic listening, thermal imaging, moisture mapping and pressure isolation all work from the surface, and the point is to narrow the leak so the repair opens one small hole rather than exploring. Occasionally an access hole is needed, and tracer gas requires draining a line — those steps should be explained before they start.

Is a smart leak sensor a substitute for professional detection?

They solve different problems. Smart water monitors and automatic shut-off valves are excellent at catching a future leak early and limiting damage. They will not locate a leak already running inside a wall or under a slab — that is what acoustic and thermal detection is for.

Should detection and repair be the same company?

Either model can work. Independence helps when you want competitive repair bids. A combined firm can be faster and may credit the detection fee. What you must have either way is a written location you can verify and, if needed, take elsewhere.

What if they cannot find the leak on the first visit?

Ask that policy before booking. Some leaks need a second visit, different isolation, or tracer methods. A firm that pretends every leak is found in one hour is selling certainty the physics does not always support — and you should know what you pay when the answer is “not yet.”