Tracer Gas Leak Detection Cost: Cylinder Plus Hours

What does a tracer gas survey cost?

The charge has two parts. The hourly rate is £180 an hour, and that is a fixed hourly rate that cannot rise on the day. The gas is charged once on top at £80, and it is declared before the team travels. No VAT is charged.

The standard rate is also £180 an hour, so choosing gas does not raise the hourly price. A visit that uses gas costs the standard visit plus £80, once.

If the leak sits in one property, the £580 package is the other route, and the tracer gas work sits inside that one price under the default scope. The tracer gas service page explains the method itself, and whether the method changes the price compares it with the other methods.

A worked example in hours

Take a leak thought to be in a heating or hot water pipe run that goes under a screed floor. The example is an illustration with chosen numbers, not a customer and not an average.

Hour one is set-up and a pressure test of each run to find out which one is losing pressure. Hour two is isolating that run, displacing the water and filling it with gas from one cylinder. Hour three is sweeping the floor surface (the notes on what a gas rig looks like on site show the equipment), skirting lines and any voids with the detector until readings peak at one point. The total is three hours at the tracer rate plus the gas charge once.

Set against the package, this example has already passed it: with the gas charge the hourly route reaches the package at about 2.8 hours. A visit that finished inside two and a half hours would have been cheaper hourly. The numbers are on the break-even page.

When is adding gas worth it?

Gas earns its cylinder when the pipe is hidden and the other signals disagree. A moisture reading that spreads across a room, a thermal image that is ambiguous because the floor is thick, and an acoustic survey that is muddy on plastic pipe are the usual cases. In each, gas gives a single peak at the escape point rather than a wide damp area.

Gas is poor value when the leak is visible, when water is running and can be heard through a clear metal pipe, or when a pressure test already isolates the fault to one short accessible joint. Paying for a cylinder to confirm what a pressure gauge showed adds cost and no information.

The pipe material is a reason to prefer gas. Published research on buried plastic pipe reports that leak noise travels less far than in metal pipe and sits at low frequency, so listening alone can be unreliable on plastic. Gas does not depend on that sound.

What tracer gas cannot do

Gas has to reach the surface to be measured. A sealed slab, a thick screed with a damp-proof membrane or a floor covering with no air path can hold gas back or spread it sideways, so the reading may be strongest a little away from the true leak. That is why the team confirms the peak against another method.

Gas does not find a leak in a pipe that is not under test, and it does not help with water that has already travelled a long way. It locates a pipe fault, not damp, and what happens once the fault is placed is covered in leak repair after detection. For the arrangement of methods on one visit see how the instruments combine.

Is the gas safe to have in the building?

The usual tracer mix is about five percent hydrogen in nitrogen, known as forming gas; the choice between it and helium is covered in forming gas versus helium. An industrial gas supplier describes hydrogen mixtures below 5.7 percent as non-flammable, and hydrogen as non-toxic and non-corrosive. Tracer gas is not mains gas, and a smell of gas is a different matter. Can you smell gas? Open doors and windows, leave switches and flames alone, get everyone outside, then use the free line for the National Gas Emergency Service: 0800 111 999. Ring them before anyone else.

Sources

Air Products, portable leak detection pages, on hydrogen mixtures below 5.7 percent being non-flammable, checked October 2026. Hunaidi and colleagues at the National Research Council of Canada, and Gao, Brennan, Joseph, Muggleton and Hunaidi, Journal of Sound and Vibration, 2004, on leak noise in buried plastic pipe, checked October 2026. Prices are the company's own.