Hidden leaks are located by narrowing systematically – isolating sections to prove which circuit is losing water, then using acoustic, thermal or tracer methods to pinpoint it. The alternative is lifting floors and opening ceilings on a guess, which is how a small repair becomes a large one.
The signs of a hidden leak
- A water bill that has climbed for no reason you can explain. On a meter, this is the most reliable early warning there is.
- A damp patch that will not dry, particularly one that does not correlate with rain.
- Warm spots on a floor, which on a heating system usually means a leaking pipe in the screed.
- Boiler pressure that keeps dropping and has to be topped up regularly. A sealed heating system should not lose water. If it does, it is going somewhere.
- The sound of running water when nothing is running. Stand still in a quiet house at night and listen – it is a genuinely useful diagnostic.
- Musty smell, or mould appearing in one specific area.
- An unvented cylinder or boiler that keeps discharging, which is a different fault but presents as unexplained water.
- Lush growth or a persistently wet patch on a lawn or drive above the incoming supply.
Turn off every water-using appliance, then note your meter reading. Do not use any water for an hour or two. If the reading has moved, you are losing water somewhere between the meter and the house. Then turn the internal stopcock off and repeat – if the meter still moves, the leak is in the supply pipe underground, before it reaches the house. This single test narrows the search enormously and costs nothing.
How we actually find it
Isolation and pressure testing
The most useful technique and the least glamorous. Sections of pipework are isolated in turn and each is pressure tested. A section that holds pressure is eliminated; a section that does not is where the leak is. On a heating system this means isolating circuits; on plumbing it means isolating hot, cold, and individual branches. It is methodical rather than clever, and it narrows a whole house down to a few metres of pipe.
Acoustic detection
A pressurised leak makes a noise – a specific broadband hiss as water escapes through a small orifice. Acoustic equipment amplifies that and lets you follow it to its loudest point. It works extremely well on pressurised mains and buried supply pipes, and less well on gravity systems and very slow leaks where there simply is not enough energy to make a sound.
Thermal imaging
A thermal camera shows temperature differences at the surface. It finds leaking hot pipes under floors and in walls very effectively, because the heat plume is visible long before the damp is. It also shows evaporative cooling from damp areas, which helps map the extent of what has got wet. It sees surface temperature, not through walls, so it is an aid rather than an x-ray.
Tracer gas
Where nothing else works, a safe inert gas mixture is introduced into the drained pipework and a sensitive detector follows it to where it escapes. It is the technique that finds leaks nothing else will, because gas will travel through material that water leaks too slowly to reveal.
Moisture mapping
Non-invasive and pin-type moisture meters establish where the water has actually spread, which matters both for finding the source and for knowing what will need drying afterwards.
Heating system leaks specifically
A sealed central heating system that needs topping up is losing water, and it is worth taking seriously for reasons beyond the water itself. Every top-up introduces fresh, oxygenated water into a system designed to hold the same water indefinitely. Oxygen is what corrodes steel radiators from the inside, and the resulting magnetite is what blocks heat exchangers and pumps. So a slow leak that gets topped up monthly is quietly destroying the system.
The usual sources, in order:
- The pressure relief valve discharging, which is usually a failed expansion vessel rather than a leak at all. Check the outside discharge pipe for drips – this accounts for a large share of ‘mystery’ pressure loss.
- A radiator valve gland weeping – often too slowly to make a puddle, but enough to drop pressure over weeks.
- A corroded radiator, usually at the bottom, showing as a rusty weep rather than a drip.
- A leak in buried pipework, particularly under solid floors and in screeded underfloor heating.
- The boiler itself – a heat exchanger, an auto air vent, or a pump head gasket.
Boiler pressure dropping? Check the outside discharge pipe first – it is free and it explains it more often than not.
What happens after we find it
Finding a leak and repairing it are two different jobs, and we will be clear about which is which. Once located, most leaks are a straightforward repair. The awkward ones are those in screed or under solid floors, where the options are to break out and repair, or to abandon that run and re-route above ground. We will lay out both honestly with the disruption and cost implications of each, rather than defaulting to whichever suits us.
You will also get a clear written statement of what was found and where, which matters if you are claiming. Most home insurance policies now include trace-and-access cover specifically for the cost of finding a leak and repairing the damage caused by getting to it – it is worth checking your policy before you commission the work.
Questions we get asked about this
Can you find a leak without lifting the floor?
In most cases, yes – that is the entire point. Acoustic, thermal and tracer methods locate the leak so that only the affected area is opened up. Occasionally a leak in an inaccessible position still needs exploratory work, and if that is the case we will tell you before starting.
My boiler pressure keeps dropping but I cannot see any water. Where is it going?
Most often out of the pressure relief valve discharge pipe outside, because the expansion vessel has lost its charge. Go and look at the end of that pipe. If it is dry, then you are looking at a genuine leak and it needs tracing properly.
Is leak detection covered by insurance?
Frequently. Trace-and-access cover is a common feature of home insurance and is specifically intended for this. Check your policy before you commission the work, and tell us if you are claiming so the report is written appropriately.
How long does it take?
Most domestic leaks are located within a single visit. Very slow leaks, or leaks in complex or inaccessible pipework, can take longer, and occasionally a system has to be left under test and revisited.
Can you find a leak on the underground supply pipe?
Yes, and the meter test described above is what tells us to look there in the first place. Buried supply leaks are typically acoustic work. Bear in mind the pipe from the boundary to the house is normally the homeowner’s responsibility.
Will you damage my house looking for it?
That is precisely what the equipment is for avoiding. Where something has to be opened up, it is opened up at the located point, not speculatively, and you will be told before it happens.
What happens when you call
Call and describe it
You speak to an engineer, not a call centre. Most jobs can be narrowed down on the phone.
We look at it properly
A real diagnosis before a price, and a straight answer if it is not worth doing.
A written quote
Itemised, so you can see what you are paying for.
The job, and the paperwork
Certificates where the work needs them, and what will need attention next.
Where we do this work
Across Norwich and the whole of Norfolk. If you are on the edge of the county, call and ask — we will tell you honestly whether we are the right people.
- Norwich
- Wymondham
- Dereham
- Attleborough
- Aylsham
- North Walsham
- Cromer
- Diss
- Loddon
- Long Stratton
- Watton
- King's Lynn
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.