The short answer
A leak detection survey is a tidy, non-destructive visit. An engineer talks through the problem, checks your water meter, then uses methods such as acoustic listening, thermal imaging, tracer gas and moisture mapping to pinpoint the source. You receive a clear report so the repair can be targeted, with no needless digging.
If you suspect a hidden leak, the idea of someone investigating your home can feel daunting. Many people picture floors being lifted and walls opened up before anyone even knows where the problem is. A modern leak detection survey works the other way round. The whole point is to find the source first, accurately, so that any repair is small and targeted rather than a guessing game.
Here is what a typical visit looks like from start to finish, and why it stays so tidy.
It starts with a conversation, not a drill
When the engineer arrives, the first stage is an assessment. They will ask you a few questions to build a picture of what is going on. When did you first notice a problem? Is the boiler pressure dropping? Are you seeing damp patches, hearing running water, or has your water bill crept up for no obvious reason? Your answers often narrow things down before any equipment comes out of the van.
Alongside the questions comes a visual inspection. The engineer looks for the tell-tale signs of escaping water, both inside and out. Inside, that might be discoloured plaster, peeling paint, a musty smell or a warm patch on the floor. Outside, they check for pooling water or unusually soft, green ground above a pipe run. None of this is invasive. It is simply trained eyes reading the clues the property is already giving.
The water meter test
One of the simplest and most revealing checks is the meter test. With every tap, appliance and outlet switched off, the engineer watches your water meter. If the dial or digits keep ticking over when nothing is in use, water is escaping somewhere on the supply. It is a quick way to confirm whether you genuinely have a leak on the mains side and to gauge roughly how much water is being lost.
This stage helps the engineer decide which detection methods to reach for first. A steadily dropping boiler pressure points towards the heating system, for example, while a moving meter with the stop tap closed tells a different story to one that stops. It is detective work, and each result rules something in or out.
The non-invasive detection methods
No single method is right for every situation, so an engineer typically combines several. Each one has its strengths, and using them together is what makes pinpointing so reliable. Here is what each tool does.
Acoustic listening
Water escaping from a pressurised pipe makes a sound, even if it is far too faint for the human ear. Sensitive ground microphones and acoustic equipment let the engineer listen through floors, walls and hard surfaces for that distinctive hiss or rush. On longer pipe runs, a correlation technique can compare the sound reaching two sensors and calculate where the leak sits between them. This is often the method that gets closest to the exact spot.
Thermal imaging
A thermal imaging camera reads surface temperatures and shows them as a colour map. Because escaping hot or cold water changes the temperature of the surrounding floor or wall, leaks often show up as a clear hot or cool signature. It is especially useful for underfloor heating and central heating pipework, and the camera never has to touch the surface, let alone break it.
Tracer gas
For trickier leaks, the engineer may use tracer gas. A safe, non-toxic mixture, usually mostly nitrogen with a small amount of hydrogen, is introduced into the pipe. Hydrogen is the lightest molecule there is, so it finds its way out through even a hairline crack and rises to the surface, where a sensitive detector picks it up. It is a precise way to confirm a leak on pipework that other methods struggle to reach.
Moisture mapping
Damp meters and moisture sensors measure how much water is held in a wall, floor or screed. By taking readings across an area, the engineer builds a moisture map that shows where dampness is concentrated and where it is not. This helps confirm findings from the other tools and shows how far moisture has tracked from the source.
Pressure testing
Pressure testing checks whether a section of pipework is holding pressure or losing it. It is excellent for confirming that a leak exists and for isolating which part of the system is at fault, even though it does not pinpoint the exact spot on its own. Used alongside the other methods, it helps the engineer focus the search.
Signs it may be time to book a survey
- Damp patches, peeling paint or blistering plaster with no clear cause
- Boiler or heating pressure that keeps dropping
- A water meter that ticks over when everything is switched off
- The sound of running water when no taps are on
- A warm patch on the floor, or a musty smell that lingers
- An unexplained rise in your water bill
Pinpointing the source
The real skill lies in bringing all of these readings together. An acoustic trace might suggest a location, the thermal camera confirms a temperature change in the same spot, and the moisture map agrees. When the different methods point to the same place, the engineer can mark the source with confidence, often to within a small area rather than a vague region.
This is the part that protects your home. Because the leak is identified before anything is opened up, any repair can be made through a single, small access point. There is no lifting an entire floor in the hope of finding the problem underneath. Finding the leak first is what keeps the whole job tidy and proportionate.
The report you receive
At the end of the visit you should be left with a clear understanding of what was found, not just a tick in a box. A typical report sets out where the leak is, what the readings showed, and what the engineer recommends as the next step. It often includes thermal and digital images that show the evidence behind the conclusion, so you are not taking anything on trust.
This documentation matters for another reason. Many home insurance policies include cover for trace and access, which is the cost of locating and reaching a leak. A professional report can support that claim, although cover varies, so it is always worth checking the wording of your own policy with your insurer. For wider water supply questions, your provider, South West Water, can also advise on responsibility for different sections of pipe.
If you would like to understand more about how we approach this, our water leak detection service page explains the methods in more detail. You can also see the areas we cover across Devon or browse more guidance in our articles.
Frequently Asked Questions
No. The detection stage is non-destructive. The methods used, such as acoustic listening, thermal imaging, moisture mapping and tracer gas, are designed to find a leak without breaking into floors or walls. The whole purpose is to locate the source first so that any later repair is small and targeted rather than exploratory.
It depends on the property and how straightforward the leak is to find. Many surveys are completed within a few hours, with some simpler cases resolved more quickly. The engineer works methodically through the different methods until the readings agree on a location, so the time spent reflects getting an accurate result rather than rushing.
Very little. It helps to clear easy access to areas where you suspect a problem, and to note when you first spotted any signs and whether boiler pressure has been dropping. For the meter test the engineer will need every tap and appliance switched off for a short time, but they will guide you through that on the day.
Many home insurance policies include trace and access cover, which is the cost of finding and reaching a leak, and a professional report can support a claim. Cover and excess levels vary between policies, so it is always best to check the wording with your own insurer before assuming anything is included.
You receive a report explaining where the leak is, what the readings showed and what is recommended next. From there the repair can be made through a small, targeted access point. The engineer will talk you through the findings so you understand the options before any further work is arranged.
We aim to respond quickly, and same-week appointments are often available depending on demand and your location across Devon. The sooner a leak is found, the sooner damage can be limited, so it is worth getting in touch as soon as you suspect a problem. Call 07897 027775 and we will arrange a convenient time where possible.
Worried about a hidden leak in your home?
Our engineers find leaks accurately and tidily, then explain exactly what they have found. Get in touch for a clear, no-pressure quote.