Central Heating Leak Detection London
Boiler pressure keeps dropping? Radiators not heating properly? Our thermal imaging and acoustic equipment finds hidden central heating leaks in pipes, radiators, and valves without ripping up your home. Fast diagnosis, same-day repairs.
020 3912 0200Central heating leak detection finds the pipe, joint or valve that is making your boiler lose pressure, without lifting floors to look for it. We pressure test the system, then pinpoint the leak with thermal imaging and acoustic listening, adding tracer gas when the pipe is deep in concrete. Surveys in London start from £150, with an insurer-ready report included.
Why Your Central Heating Is Losing Pressure
A sealed central heating system should hold its pressure between 1 and 1.5 bar without needing to be topped up. If you are regularly adding water through the filling loop, something is wrong. In most cases, the cause is a leak somewhere in the system that is allowing water to escape faster than you might expect from even a tiny opening.
The challenge is that central heating leaks are often invisible. A pinhole leak in a pipe running under the floor might only lose a few drops per hour, but over days and weeks that adds up to significant water loss and pressure drop. The water may be absorbed by the screed, evaporate from warm surfaces, or drain away beneath the floor without ever showing on the surface.
At Leak Detect London, we use thermal imaging cameras and acoustic detection equipment to find these hidden leaks quickly and accurately. The heated water in your system creates strong thermal signatures that our cameras detect through floors and walls, while our acoustic equipment hears the sound of pressurised water escaping at the leak point.
How to Find a Leak in Your Central Heating System Yourself
Before paying for a survey, a few free checks can rule out the easy causes. Note the boiler gauge reading with the system cold, then again 24 hours later, so you know how fast the pressure is falling.
Check the Boiler and Its Discharge Pipe
Look under the boiler for drips or crusting on the fittings, then check the small copper pipe from the pressure relief valve to the outside wall. If it is wet, the valve is releasing water and the system may not be leaking at all.
Wipe Every Radiator Valve
Run a dry tissue around each valve and bleed screw. A damp tissue or a brown ring on the carpet finds a weeping valve. A pinhole in the radiator panel itself usually means a new radiator rather than a sealant.
Look Where Pipes Are Hidden
Check the airing cupboard, under the kitchen units and behind bath panels. Look for ceiling stains below upstairs pipe runs, and feel for one patch of floor that is warmer than the rest.
If nothing turns up, the leak is almost certainly in a hidden pipe. Our guide on what to do when your boiler keeps losing pressure goes through these checks in more detail.
Common Types of Central Heating Leaks
Radiator Valve Leaks
Thermostatic radiator valves and lockshield valves develop leaks over time as the internal seals and spindle packing wear. These leaks are often slow enough that the water evaporates from the warm valve body before forming a visible drip, making them difficult to spot. Our thermal cameras detect the cooled area around a weeping valve instantly.
Pipe Joint Failures
Soldered copper joints, compression fittings, and push-fit connections can all fail with age. The most problematic are joints hidden under floors, behind kitchen units, or inside wall cavities where the leak is completely invisible. We trace the full pipe route using thermal imaging and check every joint for signs of failure.
Pinhole Corrosion in Pipes
Internal corrosion causes tiny holes in copper pipes, particularly in systems where the water has not been treated with inhibitor. These pinholes are barely visible to the eye but leak enough water to drop your system pressure steadily. Older London properties with original copper pipework are particularly susceptible to this type of failure.
Under-Floor Pipe Leaks
In many London properties, particularly those built between the 1950s and 1980s, heating pipes run through concrete floor slabs. These pipes develop leaks at joints, bends, and corrosion points. Because the pipes are buried in concrete, the leak is completely hidden until the water finds its way to the surface, which can take months.
How Our Heating Leak Detection Survey Works, Step by Step
When you call us about a central heating pressure loss, our engineer follows a systematic process to identify the cause. First, we check the boiler itself for leaks at the heat exchanger, pressure relief valve, and pump connections. Many pressure loss issues originate at the boiler and can be resolved quickly.
If the boiler is sound, we test the expansion vessel to ensure it is holding its pre-charge and functioning correctly. A failed expansion vessel can mimic the symptoms of a system leak. We also check the pressure relief valve discharge pipe for signs of water, which would indicate the valve is opening and releasing water from the system.
Once we have ruled out boiler and vessel issues, we isolate sections of the system and perform pressure drop tests to narrow down which circuit contains the leak. With the leaking circuit identified, we deploy thermal imaging and acoustic equipment to pinpoint the exact location. This methodical approach saves time and ensures we find the right leak first time.
For systems with underfloor heating zones, we can isolate each zone at the manifold and test individually. This is essential for properties that have both radiator circuits and underfloor heating running from the same boiler.
What Each Heating Leak Detection Method Can and Cannot Find
Pressure Testing
Proves the system is leaking and, once each circuit is isolated, which one. It cannot say where along that circuit the water escapes, so it is the first step rather than the answer.
Thermal Imaging
Shows hot pipe routes and escaped heating water through plaster, screed and floorboards. It needs the heating running, and struggles through foil-backed insulation, thick stone floors and deep slabs.
Acoustic Detection
Hears pressurised water escaping from copper and steel pipes, even under concrete. Very small leaks, plastic pipe and background noise make the sound harder to pick out.
Tracer Gas
Finds leaks too quiet to hear or too deep to image. The leaking circuit is drained and filled with a hydrogen and nitrogen mix, which escapes at the leak and rises through the floor to a detector.
For a closer look at how the gas method works on buried heating pipes, see how tracer gas leak detection works.
System Testing and Verification
After locating and repairing the leak, we carry out a full pressure test on the system to confirm it is now watertight. We pressurise the system to 1.5 times the working pressure and monitor it for a minimum of 30 minutes. This test confirms the repair has been successful and that there are no secondary leaks elsewhere in the system.
We also check the system inhibitor levels and top up if needed. Correct water treatment is essential for preventing future corrosion and protecting the boiler, radiators, and pipework. If the system water is heavily contaminated with sludge or corrosion debris, we may recommend a powerflush to clean the system and prevent further problems. Our full water leak detection service covers all aspects of system integrity.
What Your Leak Detection Report Contains
Every survey ends with a written report. It records the pressure readings, which circuits held, the methods used, and the thermal images and photographs taken. The leak position is measured from fixed points in the room and marked on the surface so a plumber opens up in the right place.
It also sets out the likely cause and the recommended repair. Insurers handling a trace and access claim usually want exactly this information, so you can send the report on without having it rewritten.
How Much Does Central Heating Leak Detection Cost?
Central heating leak detection in London starts from £150. The figure depends on which methods the leak needs, so these are our published price ranges, including VAT:
The price depends mostly on how hard the leak is to reach. A weeping valve in a small flat sits at the bottom. Several heating zones, pipes buried in a slab, or a leak that needs tracer gas as well as imaging sits higher, and out of hours visits cost more.
You get a fixed price on the phone before we book, and the survey is no find, no fee. Our breakdown of central heating leak detection costs in London explains each factor.
How Long a Heating Leak Survey Takes
Most surveys on a flat or an average house are finished within a morning or an afternoon. Larger houses, systems with underfloor zones and leaks that need tracer gas take longer, because the circuit has to be drained, filled with gas and given time for the gas to reach the surface. If your pipes are in a solid floor, our article on central heating leaks under a concrete floor explains what to expect.
What to Do Before We Arrive
Keep a Pressure Log
Note the gauge reading each morning and every time you top up. How fast it falls shows roughly how big the leak is.
Leave the Heating On if It Is Safe
Unless water is coming through a ceiling, keep the system running and topped up to its normal pressure. A cold system gives the camera nothing to see.
Clear Access
Move rugs and furniture from the rooms where you suspect the leak, and empty the cupboards around the boiler. Have any heating plans and your insurance policy number to hand.
Central Heating Leaks in London Properties
Different types of London property have different heating system configurations and therefore different leak risk profiles. Victorian and Edwardian houses often have been retrofitted with central heating using copper pipes run through floor voids and behind plaster. These installations may be 30 to 50 years old and the pipework is reaching the end of its life.
Post-war flats and maisonettes frequently have heating pipes buried in concrete floor slabs, which are notoriously difficult to access when they develop leaks. Modern new-builds use plastic pipes with push-fit fittings, which are less prone to corrosion but can develop leaks at joints if not installed correctly.
Central Heating Leak Detection Questions
Why does my central heating keep losing pressure?
How much does central heating leak detection cost in London?
What is included in the price of a heating leak detection survey?
Can I hire central heating leak detection equipment and find the leak myself?
Do you carry out central heating leak detection in flats and apartments?
Does home insurance cover central heating leak detection?
Can you detect a leak in pipes running under a concrete floor?
Will you repair the leak once it is found?
Should I turn off the heating if I suspect a leak?
Boiler Pressure Dropping?
Stop topping up and start finding the cause. Call us for a same-day central heating leak investigation across London.
020 3912 0200Full System Diagnosis
We check the boiler, expansion vessel, pressure relief valve, and entire pipe system before deploying detection equipment. Methodical diagnosis means we find the real cause first time.
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Get a No-Obligation Leak Detection Quote
Tell us what's happening and we'll come back to you with a clear price for the investigation. No pressure, no hidden fees. Or if it's urgent, just ring us. We pick up 24/7.
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