Plumbing · Marylebone, London
Leak Detection & Repair in Marylebone, London
The hardest question in a Marylebone leak is rarely how to fix it. It is whose it is. [The Honest Plumber Marylebone](/) takes calls on 07782 221769 at any hour, and when you describe a stain, a smell of damp or a water bill that does not make sense, we arrange an independently owned partner company to find the source and tell you in plain terms where the responsibility sits.
Most buildings here are late-Georgian townhouses divided into flats, or Edwardian mansion blocks with communal risers and stacks. A drip at your ceiling may be your upstairs neighbour's shower waste, a shared riser the freeholder maintains, or your own supply pipe running through a wall. Each one has a different person paying, so the finding comes before the fixing.
Detection costs money, and we would rather you knew how much. Published UK guides put a leak-detection survey at about £150 to £750, with infrared camera work around £150 to £1,000 and tracer gas from £250 up to £2,000 for complex cases. One 2026 guide adds that London tends to run 10 to 25 per cent above that, and the partner company confirms a price in writing.
Not every damp patch is a leak. Condensation in a tight, poorly ventilated flat, a failed seal around a bath or a roof or window problem can all mimic one. A good survey rules them out, and that is a result worth paying for, because it stops you opening a wall for nothing.
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Services
Where Leaks Hide Here
The three places we are most often asked to look, and why they are tricky.
Behind Plaster in Period Houses
Georgian and Victorian houses carry lead and early copper pipework chased into walls and under boards. A pinhole in one can run for weeks before a stain appears, often a metre or more from the real fault. Thermal imaging and acoustic listening narrow the search before anyone lifts a floor or opens a wall.
Shared Risers and Stacks in Mansion Blocks
Water running down a communal riser can surface in a flat several floors from its source. The partner company traces it flat by flat where access allows, and writes down what they found. That record gives you something concrete to hand to the managing agent or freeholder instead of an argument.
Under Floors, Baths and Showers
A seeping bath waste, a failed shower tray seal or a joint under a floating floor leaves a damp ceiling in the room below. Tracer gas or a moisture meter finds it without lifting the whole floor. The related repair is covered under shower repair and burst pipe repair.
What's In It for You
How a Leak Hunt Is Run
Cheapest first, most invasive last.
Rule Things In and Out
The partner company checks your meter with everything off, looks at seals and condensation, and asks about when the problem began. Often that alone narrows a search by half.
Locate Without Demolition
Moisture meters, thermal camera, acoustic listening or tracer gas pinpoint the fault. You are told the method and its cost up front, and nothing is opened up without your say-so.
Repair, Then Reinstate
Once the leak is found, the repair is quoted in writing. Making good plaster or decoration afterwards is usually a separate trade, and we tell you so rather than let it surprise you.
Handy to Know
Signs You May Have a Hidden Leak
Check these before you ring, and tell us what you find.
Clues in the Building
Early signs are subtle.
- A brown ring or bubbling paint on a ceiling or wall
- A musty smell in a cupboard, under stairs or in a basement
- Floorboards that feel soft, cold or slightly raised
- Wallpaper lifting along a line, not in a patch
- Warm patches on a floor with no underfloor heating
Clues in the Numbers
Your meter and bills can show a leak your eyes cannot.
- A water meter dial that moves with every tap off
- A bill noticeably higher than the same quarter last year
- A boiler pressure gauge that keeps dropping
- A tank or cistern that refills when nobody has used it
- The sound of running water in a quiet, empty room
What You Can Expect
Why the Source Is Half the Job
A leak found is a bill avoided.
Standards the Work Follows
Repairs to supply pipework follow the Water Supply (Water Fittings) Regulations 1999 and BS EN 806, with WRAS-approved fittings. Drainage leaks follow Building Regulations Part H.
Honest About What Is Yours
If the fault is on a shared pipe or the building's plant, we say so in plain words. You do not pay to repair something the freeholder is responsible for.
Careful in Period Interiors
In a conservation area or listed house, finding the leak with the least disturbance protects cornicing, panelling and old floors that cost far more to restore than any pipe.
When a leak turns into a burst, see burst pipe repair. If water is already coming through, start at emergency plumbing. Everything we cover is on our services page.
Why Leaks Are Hard to Pin Down in an Old Grid
Marylebone was laid out in the eighteenth century. Manchester Square dates from 1776 to 1788 and Mansfield Street from 1770, and later estate rebuilds along Harley Street and Wimpole Street added mansion flats on top of the Georgian plan. Over two centuries pipework has been added, rerouted and abandoned behind the same walls, and water finds the weakest route, not the shortest.
The river Tyburn also ran through the old parish, and basements close to its course need particular care. Damp in a lower-ground flat is not always from a pipe at all, which is why we ask questions before sending anyone with a camera.
What Affects the Cost of Finding a Leak
Method
A moisture-meter and meter-dial check is the cheapest way to start. Thermal imaging and acoustic listening cost more, and tracer gas is reserved for the stubborn leaks where nothing else has worked. The partner company explains the choice and the price, and nothing is added without your agreement.
Access and Building Type
A leak in a single-storey ground-floor flat is simpler to trace than one inside a six-storey mansion block, where several neighbours and a managing agent are involved. Central London adds parking and permit costs, and Westminster's conservation-area rules can affect how and where an opening is made.
The Repair Itself
Once found, many repairs are small. A failed compression joint or a worn tap washer costs a fraction of the survey. A cracked section of lead pipe, or a leak under a solid floor, costs more, and the partner company tells you which it is before quoting. If a pipe is beyond economical repair, they will say so and discuss options.
Whose Leak Is It? The Plain Version
Your Pipe, Your Problem
Pipework that serves only your flat, from the point it enters your front door or your isolation valve, is normally yours to repair. That includes the fittings behind your own bath, your basin and your kitchen. If the partner company finds the fault there, you approve a written quote and they fix it.
The Building's Pipe, the Building's Problem
Shared risers, communal tanks and the stacks that carry waste from several flats generally belong to the freeholder or managing agent, and your lease says so in more detail. If the partner company finds the source on one of those, ask them to put it in writing: the location, the pipe and the flats it serves. You then pass that to your agent and ask them to arrange the repair.
When a Neighbour Is Involved
A leak from the flat above is awkward. Ring the managing agent first and keep your photographs dated. The partner company can attend your side, record the damage and, where the neighbour consents, trace the fault upstairs. Our contact page is the quickest route if you want to discuss which situation you are in.
Good Questions
How much does leak detection cost in London?
Published UK guides put a basic leak-detection survey at about £150 to £750, with infrared camera work around £150 to £1,000 and tracer gas from about £250 to £2,000 for complex cases. One guide adds 10 to 25 per cent for London. These are ranges, not our quote. The partner company confirms its figure in writing before starting any survey.
How do I tell whether the leak is mine or my neighbour's?
Turn everything off in your flat and watch your meter or boiler pressure. If the dial still moves, the leak is probably on your supply. If it does not, the water may be coming from a neighbour's pipe, a shared riser or the roof. The partner company can test and write down what they find, which gives you evidence to raise with the managing agent.
Who pays when a shared pipe in a mansion block leaks?
Usually the freeholder or managing agent, because communal risers and stacks belong to the building and not to any one flat. Your lease sets out the detail, so read it or ask your agent. The partner company will say in writing where the pipe sits and who it serves, so that you are not paying for something that is not yours to fix.
Will you need to lift floorboards or open the walls?
Only as a last step. Moisture meters, thermal cameras, acoustic listening and tracer gas locate most leaks without demolition. When access is needed, the partner company opens the smallest area possible and tells you first, so nothing is cut without your agreement. In listed or conservation-area buildings, preserving cornices, panelling and original floors is part of the brief.
My water bill has jumped. Could that be a hidden leak?
It could. Check that your meter dial moves with every tap and appliance off, since a moving dial points to a leak between the meter and the taps. A running toilet cistern is the commonest cause, followed by a leaking underground supply pipe. If the dial is still, the cause is probably usage or an estimated bill, and a survey would be wasted money.
Can limescale cause leaks in Marylebone?
Yes. Thames Water supplies hard water, and its 2025 figure for the nearest published zone was 266 mg/l of calcium carbonate. Scale builds on valves, tap seats and shower cartridges, stops them sealing and makes them drip. It also clogs isolation valves so they will not shut during a leak. Descaling or replacing a valve is often the cheap, honest fix.
Is a damp patch always a leak?
No. Condensation, a failed bath seal, blocked gutters, a faulty window or rising damp can all produce similar marks. A good survey starts by ruling those out. If the water is not from a pipe, the partner company says so and recommends the right trade, which avoids you paying to open up a wall that was never leaking.
How long does a leak survey take?
A straightforward survey with meters and a thermal camera can take an hour or two. Tracing a leak through a mansion block's riser may take longer, because access depends on neighbours and the managing agent. The partner company gives you an honest estimate on the day, and does not promise a finish time before seeing the building.
Do you also repair what you find?
The partner company can usually repair the leak on the same visit or return with parts. The repair is quoted separately in writing, so you can decide before work starts. Making good plaster, tiling or decoration afterwards is normally another trade, and we say that at the outset. See emergency plumbing if water is actively flowing.
Will the survey cause a mess in my flat?
Surveying itself is clean. Moisture meters, cameras and listening equipment leave no marks, and tracer gas is introduced through the pipework. If something has to be opened, the partner company protects floors, tells you the size of opening first and leaves the area tidy. Mansion blocks may also require notice to the managing agent for access to communal areas.
Do you cover Fitzrovia, Mayfair and St John's Wood too?
Yes. We cover Marylebone, Fitzrovia, Mayfair, St John's Wood, Regent's Park and Portland Place. Ring 07782 221769 and give us the postcode, and we match the partner company nearest to you that suits a leak hunt. Pages for Mayfair and Fitzrovia describe the building types we most often see there, and the same survey methods apply in every one of those areas.
Stain on the Ceiling? Let Us Find Where It Starts
Written quote first. Call 07782 221769.
07782 221769