Leak Detection and Repair: Which Service Do You Need?

Leak detection and leak repair answer different questions. Detection asks where water is escaping and what evidence supports that conclusion. Repair asks what work will stop it and how the result will be checked. You may need both, but that does not mean every dripping joint requires a specialist survey or every detection visit includes opening a floor and replacing pipework.

The right booking begins with a description of the problem. Say whether water is actively escaping, whether the source is visible, which rooms are affected and whether anything has already been isolated. A clear starting account helps the contractor propose an appropriate first visit. It also makes it easier to compare quotations that might otherwise describe very different services with the same phrase, “leak detection and repair”.

What does leak detection include?

A detection visit is an investigation. It may start with a visual assessment and a review of the symptoms before the contractor chooses any tests. Ask which parts of the installation are included: the incoming supply, internal hot and cold pipes, heating pipework or a particular room. A survey of one system should not be described as proof that every other system in the building is sound.

Contractors may propose acoustic equipment, thermal imaging or pressure tests, depending on the suspected source and conditions. Ask them to explain the purpose of each proposed method and what it can establish in your property. Do not select a package solely because it lists more devices. The useful outcome is a supported finding and a practical next step, rather than a collection of images that nobody has interpreted.

The report should distinguish a confirmed leaking component from an area that needs further access. An engineer may narrow the search without exposing the actual fault during the first appointment. Discuss that possibility before booking, including how an inconclusive visit is charged and what would trigger additional work. A professional investigation can reduce uncertainty; it should not be sold as a guarantee that no exploratory access will ever be needed.

For example, a damp ceiling tells you where moisture has appeared, but it does not by itself establish which fitting or pipe needs repair. Give the contractor information about the rooms above, recent plumbing work and when the mark changes. Those observations can guide an assessment without claiming that a particular system is definitely responsible. If the room above is a bathroom, our guide to a leaking bath explains four simple tests that narrow down the source.

What does leak repair include?

Repair is the work needed to address the identified fault. The scope might involve an accessible fitting, a section of pipe or a component that requires access behind a panel. Ask the contractor to identify the proposed repair, explain whether it is temporary or permanent, and state what testing will follow. These details matter more than the general assurance that the leak will be “sorted”.

Access and reinstatement need their own discussion. A plumber may be able to repair a pipe once another trade opens a tiled enclosure, while restoring tiles and decoration may be a later job. Alternatively, one contractor may quote for the complete sequence. Neither arrangement is automatically better, but your quotation should make the responsibilities explicit.

For an active burst or significant escape of water, stopping further damage takes priority over collecting perfect documentation. If you know the correct accessible isolation valve and can operate it safely, isolate the supply; do not force a seized valve or operate an unidentified shared one. Keep away from water near electrical equipment and arrange urgent professional help. Our burst pipe repair service is the appropriate route to discuss an active water emergency.

When immediate work only isolates a damaged section, ask what remains out of use and what the permanent repair requires. Keep that information in writing. A temporary measure can be a sensible first step, but it should not be mistaken for a finished job when arranging follow-up work, notifying a landlord or discussing an insurance claim.

Compare the scope before comparing the price

There is no reliable single price for all London leak investigations. A visible connection in a kitchen cupboard and a suspected buried supply leak do not require the same visit. Ask for the current charge for your proposed scope rather than treating an online “typical cost” as a binding quotation. The property, access, urgency and work authorised all matter.

Part of the job	Question to ask	What to get in writing
Attendance	Is this a call-out charge, an hourly appointment or a defined investigation?	Minimum charge, included time and VAT treatment
Detection	Which system and areas will be investigated?	Scope, access assumptions and report provision
Opening access	Who authorises and carries out any opening work?	Extent of access and exclusions
Repair	Can the identified fault be repaired during this visit?	Labour, parts and any additional attendance
Testing	How will the repaired section be checked?	Result and any remaining limitations
Making good	Who restores floors, walls and decoration?	Included finishes and separate trade work

For a time-based job, agree how the contractor will seek approval if more time or a different method is needed. For a fixed-scope service, ask what happens if the suspected pipe cannot be accessed or the leak does not occur during the appointment. These are ordinary planning questions. Clear answers help you make a decision without assuming that every uncertainty will become an unlimited extra charge.

Our published call-out policy is £60 for short diagnostic visits, waived on jobs taking over two hours. Confirm how that applies to the particular service when booking; specialist investigation work may have a separately agreed scope and price. Do not assume a fee waiver also includes parts, a report, excavation or the cost of restoring a floor.

Which service should you ask for first?

If water is visibly escaping from an accessible fitting, describe it and ask for a repair assessment. Send a clear photograph if requested, without moving unsafe objects or dismantling anything. The plumber still needs to establish the condition and correct repair, but a separate concealed-leak package may not be relevant.

If you have unexplained moisture, repeated water loss or an unexpectedly high metered bill, request an investigation and explain the evidence. Thames Water's leak identification guidance includes unexpected usage, reduced pressure and damp ground among signs to investigate. Those signs should prompt assessment; they do not individually identify a failed pipe or rule out another cause.

When a bill is the main concern, keep the actual readings, billing dates and any supplier messages. Check whether the bill is based on estimated readings and note changes in occupancy or water use. Tell the contractor if a toilet appears to run continuously or an appliance has recently changed. A high bill should not automatically lead to opening floors before accessible fixtures and the account information have been considered.

If the problem affects pressure rather than a visible escape, explain whether hot water, cold water or both are affected and whether neighbours have the same experience. Our low water pressure guide covers that separate starting symptom. Book according to the actual observations rather than choosing a service name because it appeared first in a search result.

Prepare a short handover for the engineer

Write a timeline with the first sign of the problem, later changes and any action taken. Distinguish the date a stain appeared from the date you think a leak might have started. If you do not know, say so. An honest gap is more useful than an estimated date presented as a measured fact.

Photograph visible damage and retain the originals. Include enough of the surrounding room to show where a close-up was taken. Keep previous invoices and reports available, especially if another contractor has already tested part of the system. Tell the engineer which rooms or cupboards are accessible and who can authorise opening work if it is needed.

In a flat, record the floor level and explain whether the suspected area is inside your home, in a communal riser or in another flat. Arrange access through the appropriate resident or managing agent. Do not operate shared isolation equipment without knowing whom it serves. A visit can be delayed if the only accessible section is in a locked area that nobody has arranged to open.

Also describe what would make the visit successful for you: finding the source, stopping an active leak, obtaining a report for the next contractor, or confirming the next investigation stage. These objectives overlap but are not identical. Put the agreed scope in the booking confirmation so both sides start with the same expectations.

Keep repair, insurance and water allowances separate

A contractor can record findings and work carried out, but cannot decide whether your insurer must pay. Before commissioning non-urgent insured work, ask the insurer about approval, required evidence, applicable limits and any excess. Record the response. Urgent action to limit ongoing damage may still be necessary; document what was done and notify the insurer promptly.

The Financial Ombudsman Service's gradual damage guidance explains that it considers policy wording, reports, photographs and the circumstances of individual complaints. It discusses situations in which concealed damage may merit a different assessment from damage someone could reasonably have noticed. That is not a promise that a report or a hidden pipe will make every claim payable.

A water-bill allowance is another separate process. Our Thames Water household leak allowance guide explains how to organise repair evidence and account records. Do not delay repairing an active leak while waiting to build an allowance file, and do not assume a credit for lost metered water reimburses investigation or building repairs.

Before commissioning work you expect to claim, use our trace-and-access insurance checklist to organise the approval questions, scope and evidence.

Check pipe responsibility before authorising major work

Thames Water distinguishes its mains and communication pipes from customer supply pipes and internal plumbing. Its responsibility guidance also addresses shared supplies and pipes crossing someone else's land. A boundary assumption can therefore be too simple for some properties. Ask the supplier to clarify an uncertain arrangement before commissioning major excavation.

If you rent, report the problem to your landlord or letting agent promptly and keep a written record. If several properties share the relevant section, coordinate the investigation and access before work begins. The plumber's findings can describe the physical fault, but ownership disputes or payment arrangements may require a separate discussion between the relevant parties.

Handing an investigation to a different repair contractor

Send the full report rather than only the final page or a photograph of a marked floor. Include the areas tested, any access restrictions and the investigator’s explanation of uncertain findings. Ask the repair contractor to review that information before quoting. If they recommend a different access point, ask what new evidence supports the change. Keep one shared record of the work so an insurer, managing agent or later contractor can distinguish the original investigation from subsequent discoveries.

You have a leak but cannot find it: what to do first

This is the most common starting point for a detection booking, and a few simple checks make the visit more focused. None of them need tools.

1. Check the meter. If you have a water meter, turn off every tap and water-using appliance, make sure nobody uses water, and read the meter. Read it again after an hour or so. If the numbers have moved, water is escaping somewhere on your side of the meter. Thames Water's guidance describes the same test.
2. Watch the boiler pressure. On a sealed heating system, pressure that keeps falling with no visible drip points to a leak on the heating pipework rather than the water supply. That changes which pipes need testing.
3. Listen for the toilet. A cistern that trickles into the pan all the time is a very common cause of lost water and is easy to miss. Our guide to a toilet running constantly covers the fix.
4. Note when the damp changes. A stain that grows after showers suggests the shower or its seals. One that stays wet regardless of use points towards a pressurised pipe.

Write down what you find and pass it on when you book. It will often decide whether the first visit is a repair or an investigation.

How professionals find hidden leaks

A plumber can carry out leak detection, and for many domestic leaks a competent plumber with basic test equipment finds the source. The methods most often used are:

• Pressure testing a section of pipework to confirm whether it holds pressure, which narrows the search to a particular circuit.
• Thermal imaging, which shows warm water escaping from heating or hot water pipes as a temperature pattern on a floor or wall.
• Acoustic listening, which picks up the sound of water escaping under pressure through floors and screed.
• Tracer gas, where a safe gas mix is put into a drained pipe and detected where it comes through the surface. It is used when a pipe is deep or the other methods are inconclusive.
• Moisture readings and dye tests, which are useful for showers, baths and waste pipes that only leak when in use.

No single method suits every leak, which is why the booking questions above matter. Our leak detection service page explains which of these we use and when, and the water leak detection guide goes into the process in more detail.

Common leak repairs once the source is found

Where the leak is	Usual repair
Compression or push-fit joint under a sink or bath	Remake or replace the fitting, then test
Pinhole in a copper pipe	Cut out the damaged section and fit a new length
Pipe under a floor or in a wall	Open access at the confirmed point, repair, pressure test, then make good
Shower tray, enclosure or tiled wall	Replace failed seals or trap, or repair the tray; see leaking shower repair
Radiator valve or heating pipe	Repair the valve or joint and repressurise the system; see radiator valve leaking
Supply pipe between the boundary and the house	Repair or replace the section; check responsibility first

For a leak you can already see, go straight to our water leak repair service rather than booking a detection visit.

Common questions

Can a plumber do leak detection?

Yes. Many domestic leaks are found by a plumber using pressure tests, moisture readings and a careful look at the likely fittings. Specialist equipment such as thermal imaging, acoustic listening or tracer gas is brought in when the pipe is buried in a floor or wall, or when simpler tests do not narrow it down. Ask what methods the visit includes when you book.

Can one contractor detect and repair the leak?

Sometimes, but confirm this before booking. The required equipment, access, parts and available time depend on the job. Ask whether a repair can be quoted after the initial findings, whether another appointment may be required and how the investigation records will be handed over if a different contractor completes the work.

Does a detection report guarantee the exact leak location?

No. Ask the report to state what was confirmed, what was inferred and which areas remain untested. If the contractor has only narrowed the likely area, the next access stage should reflect that uncertainty. Clear limits make a report more useful to the repair contractor and help prevent unsupported assumptions being repeated.

What should I receive after a repair?

Ask for the fault description, location, work completed, date and relevant test result. Keep any photographs and the invoice. If the repair was temporary, the record should say so and identify the follow-up needed. Do not ask the contractor to change factual findings merely to fit wording you believe an insurer prefers.

What if the first visit finds no leak?

Request a record of the systems checked and the conditions at the time. Ask what would justify further investigation and what alternative assessment may be appropriate. Keep monitoring the original symptom without carrying out unsafe experiments. An inconclusive visit should lead to a reasoned next step, rather than an automatic repeat of the same package.

When the first clue is a higher water bill

Before booking an investigation based only on the amount payable, use our high water bill with no visible leak guide. It explains how to compare actual daily use, distinguish estimated readings and prepare evidence for a focused enquiry.