Leak detection is a survey that pinpoints where water is escaping from a pipe you cannot see, so that only the small area directly above the fault is opened up. Instead of lifting a whole floor or cutting into several walls on a hunch, the engineer uses thermal imaging, acoustic listening equipment, tracer gas and moisture readings to narrow the search down to a single point, then marks it for repair.
The method chosen depends on the pipe. A leaking heating or hot water pipe shows up as warmth on a thermal camera. A pressurised cold main under a solid floor is usually found by sound. A very slow leak below screed or behind tiles may need tracer gas. Most visits use more than one of these, because each confirms what the others suggest.
Before anyone arrives
The call beforehand matters more than people expect. You will be asked what you have noticed, when it started and which systems might be involved: is the boiler losing pressure, is the water meter turning with every tap off, is there a damp patch, a warm spot on the floor or a sound of running water at night? Those answers decide which equipment comes on the visit and which parts of the house get checked first.
It helps to note the boiler pressure over a couple of days, take a meter reading last thing at night and again first thing in the morning without using any water, and photograph any staining as it spreads. None of that needs tools, and it shortens the search.
The methods, in plain terms
- Thermal imaging: a camera shows temperature differences, so a leaking heating, hot water or underfloor pipe appears as a warm plume spreading where it should not.
- Acoustic listening: water forced out of a pressurised pipe makes a noise, and sensitive ground microphones and correlators locate where that noise is loudest.
- Tracer gas: a safe hydrogen and nitrogen mix is put into a drained pipe; it escapes through the fault and is picked up at the surface by a detector.
- Moisture mapping: meters track how wet walls and floors are, which shows the direction the water is travelling from its source.
- Pressure testing: isolating sections of pipework and watching whether each holds pressure confirms which run contains the leak.
What the visit looks like
The engineer starts by confirming there is a leak and which system it is on, usually with a pressure test. That step alone sometimes changes the picture: a boiler losing pressure can be a faulty relief valve discharging outside rather than a pipe leaking under the floor.
Once the system is known, the search narrows room by room. The point found is marked on the floor or wall, and you are shown the evidence, whether that is a thermal image or a clear peak on the acoustic reading. On our visits the repair can follow on from the detection, so you are not left finding a second trade to open up and fix what has just been located.
Why not just start digging?
Water travels. It runs along joists, follows pipe sleeves and soaks through screed, so the damp patch you can see is often some distance from the actual fault. Opening up where the stain is can mean lifting a finished floor and still not finding the leak. A targeted survey usually costs far less in disruption than a search by demolition, particularly with tiled floors, kitchens fitted over pipework or underfloor heating.
Insurance and paperwork
Many home insurance policies include trace and access cover, which pays towards finding a leak and opening up to reach it. Check your policy wording before the visit. We provide a written report with images from the survey that you can pass to your insurer with your claim.
When it is urgent
If water is coming through a ceiling or you cannot stop it, this is no longer a survey job. Turn the water off at the stop tap, switch off electrics near the water if it is safe to do so and call an emergency plumber first. Our guide to turning off your water shows where to look.
Frequently asked questions
- Will you have to lift my floor?
- Only directly above the leak once it has been located, usually a single tile or floorboard. The purpose of thermal and acoustic detection is to avoid the wider lift that guesswork causes.
- Can you find a leak in underfloor heating?
- Yes. Underfloor pipes carry warm water, so thermal imaging is often the quickest way to see where a loop is leaking once the system is running.
- Is tracer gas safe in my home?
- The gas used is a hydrogen and nitrogen mix commonly used in leak detection. It is introduced into drained pipework and escapes in small amounts at the fault.
- Can the leak be fixed on the same visit?
- Most accessible pipe leaks can be repaired on the same visit. Some underfloor heating repairs need a return visit if a specialist coupling has to be ordered, but the leak is isolated straight away.
- How much does leak detection cost?
- It depends on the symptoms, access and method needed. We confirm the scope and charge before the survey, then quote separately for any repair.
Think you have a hidden leak?
Tell us what you have noticed and we will explain which method suits your home.