THE SHORT ANSWER
What is leaking, and what should you do first?
Water around an exposed pipe may come from a supply line, waste pipe, heating circuit, joint or valve; the wet point alone does not prove the cause. If water is spreading, keep clear and check the urgency guidance. From a dry safe position, note the first visible point and what was already happening. A known private inside stop tap may limit incoming mains water, but stored water or a heating circuit can continue.
Jump to a section
Is the water causing damage now?
| What you already notice | What it may mean | Next step |
|---|---|---|
| Water is spreading, pouring or pooling | The leak may be uncontrolled and can damage the property. | Keep clear. Use the known private inside stop-tap action only if its conditions apply; call for urgent plumbing help. |
| Water is reaching or approaching electrical equipment or exposed wiring | There may be an electrical hazard. | Do not touch wet electrical equipment or wiring. Keep clear and seek urgent help; affected equipment needs an electrician. |
| A small drip or damp patch is contained and away from electrics | It may not be an immediate emergency, but a recurring leak still needs attention. | Record it from a dry position and arrange prompt assessment. |
| Water is coming through a ceiling, wall or floor | The source may be hidden and could be in another room or property. | Do not open the surface or enter a wet space; contact the landlord/building manager or plumber promptly. Escalate if spreading or near electrics. |
| You are unsure how much is leaking or which system it belongs to | The visible water alone cannot identify the source. | Stop checking if access is wet or uncertain. Report what you have already seen and seek help. |
Keep clear around water and electrics
Do not touch water-damaged electrical equipment, exposed wiring or wet fittings. This guide does not give electrical isolation instructions. If water has reached electrical equipment, keep people clear and arrange suitable electrical assessment.
Sources
- WaterSafe Register - What should I do if a water pipe bursts?
- Thames Water Utilities Limited - Find and use your inside stop valve
- WaterSafe Register - What to do with a leak under your sink
- Electrical Safety First - Electrical safety after a flood
- Drinking Water Inspectorate - Water storage tanks and cisterns
- Association of Plumbing & Heating Contractors (APHC) - Dealing with plumbing and heating emergencies
Where does the water first appear?
| What you already observed | Possible route | Useful next step |
|---|---|---|
| Water visibly appears at an exposed pipe body | A supply, waste or heating pipe may be involved. | Note the location and whether water is still escaping; do not touch or seal it. |
| Water first appears around a joint or connection | A connection is a visible location, not a confirmed failed part; water may have travelled from above. | Record it from a dry position without tightening or moving the pipe. |
| Water is at a valve or valve connection | It may be a local or system valve; its purpose and the source are not established by appearance. | Do not operate it unless it is positively identified as your private inside stop tap and the safe conditions below apply. |
| Water appears near a sink waste/trap during or after ordinary drainage | A waste route is possible; timing alone is not proof. | Do not run the sink to test it. Use the under-sink guide if that is where the water is visible. |
| Water is by a radiator/heating pipe or the heating gauge already shows a repeated pressure drop | A heating circuit may be involved; a pressure change can have other causes. | Do not top up or repair from this clue; contact a heating engineer. |
| You cannot see the first wet point, or water is in a wall/floor/ceiling | The source may be hidden or the water may have travelled. | Do not open the building surface; arrange assessment and report the uncertainty. |
Supply pipes carry water towards fixtures; waste pipes carry used water away. A supply-side leak may be noticed while a fixture is idle, while a waste leak may become apparent during or after normal drainage. These are clues only, and the timing example is not a test. Do not turn taps on, drain fixtures, run appliances or switch the heating on to recreate a leak.
What can you safely do before help arrives?
Stay on dry ground
Look only from a dry, safe position. Note where water first appeared and whether it is still escaping, spreading or near electrical equipment.
Catch a visible drip if safe
If it can be reached without going through water, touching a fitting or approaching electrics, place a stable container underneath or use towels on the floor. Stop if water spreads or access becomes wet.
Use only a known private inside stop tap
For an active incoming mains leak, and only if positively identified, private and safely reachable from a dry position, turn the conventional inside stop tap clockwise by hand until it closes normally. Do not use force, tools or a shared/unfamiliar valve.
Check from a safe position
Incoming water may take a few minutes to stop; stored hot water or a separate heating circuit may continue. If water continues or the system is uncertain, do not try other valves; call a plumber or heating engineer. Leave a closed stop tap closed until the leak is assessed.
This is damage limitation, not a repair
Do not tighten a joint, wrap it with tape, apply sealant, clamp or cut a pipe based on a visible drip. Pipe materials, joints and system types vary; stop-tap closure does not repair the leak.
Sources
- WaterSafe Register - What should I do if a water pipe bursts?
- Thames Water Utilities Limited - Find and use your inside stop valve
- WaterSafe Register - What to do with a leak under your sink
- Electrical Safety First - Electrical safety after a flood
- Vaillant UK - Why is my boiler losing pressure?
- Drinking Water Inspectorate - Water storage tanks and cisterns
- Association of Plumbing & Heating Contractors (APHC) - Dealing with plumbing and heating emergencies
How can you tell which system may be involved?
Water to a fixture
Supply water
A supply pipe brings water to a tap, toilet or appliance. If the leak was already visible while the fixture was idle, tell the plumber; this timing does not prove a supply fault. An inside stop tap may limit incoming mains water only when the strict conditions above apply.
Water away from a fixture
Waste water
Waste pipes carry used water away from sinks, baths and appliances. A leak noticed during or after ordinary draining may be on this route, but do not deliberately run water or dismantle a trap to check.
Radiator and heating circuit
Central heating
If a visible leak is beside a radiator or heating pipe, or a sealed system’s pressure gauge is already dropping repeatedly, report that clue to a heating engineer. Low pressure does not locate a leak and can have other causes. Do not remove a boiler cover or top up to conceal a leak.
A household may have stored hot water and separate valves or circuits. A private inside stop tap controls incoming mains water, not every water route in a home. If you are not sure which system you can see, do not operate its valve.
Leak beneath a sink?
If ordinary sink use is sending water through the leaking waste route, stop using that sink. If an appliance discharges into the affected route, leave it out of use too; do not disconnect it. Our under-sink guide helps distinguish supply connections from the waste outlet and trap.
Choose the guide for the observed pattern
Use the joint guide for a visible connection concern, the moisture guide for unexplained surface wetness, or the heating-pressure guide for a repeatedly falling sealed-boiler display. None of these clues alone identifies the leak source.
Sources
- WaterSafe Register - What should I do if a water pipe bursts?
- Thames Water Utilities Limited - Find and use your inside stop valve
- WaterSafe Register - What to do with a leak under your sink
- Hightown Housing Association - Repairs Handbook
- Vaillant UK - Why is my boiler losing pressure?
- Drinking Water Inspectorate - Water storage tanks and cisterns
- Association of Plumbing & Heating Contractors (APHC) - Dealing with plumbing and heating emergencies
Why might a pipe start leaking?
The faulty part may be a seal or connection rather than the pipe itself. Under a sink, examples include worn washers, perished seals and loose fittings. A knock from stored items can disturb pipework, while a poorly aligned plastic waste pipe may crack or slip. These examples help describe the problem; they do not tell you which fitting to tighten.
On heating pipework, corrosion or a connection that has loosened can allow water to escape. Condensation can also leave a pipe wet, so surface moisture alone does not confirm a leak. Tell the repairer whether you saw a definite drip from one point, wider surface dampness or a pressure change; do not touch a potentially hot pipe to investigate.
Which part might need replacing?
Possible work ranges from a compatible washer or seal to a fitting, waste-pipe section or damaged pipe. The pipe material, diameter, connection and system must be identified before choosing parts. A generic roll of tape or an extra turn of a nut is not a diagnosis.
Should you try to repair the pipe yourself?
This guide supports visual triage and immediate damage limitation; it does not provide a generic pipe repair. A pipe body, joint, valve, waste line and heating circuit can require different parts and isolation. A visible leak point does not identify a compatible repair.
Arrange a plumber for a continuing visible leak, a burst or damaged pipe, an uncertain supply, or a repair that needs a fitting to be loosened or replaced. For radiator/heating pipework, contact a heating engineer. If water appears to be coming from inside a gas boiler, use a Gas Safe registered engineer and leave the casing closed. If you rent or live in a managed building, report the leak to the landlord or building manager promptly.
If the leak seems to be on an outside supply pipe in England or Wales, ask your water company who is responsible and whether it offers one-off help. CCW describes the customer supply pipe as running to the property boundary, but company arrangements vary.
Sources
- WaterSafe Register - What should I do if a water pipe bursts?
- Thames Water Utilities Limited - Find and use your inside stop valve
- WaterSafe Register - What to do with a leak under your sink
- Hightown Housing Association - Repairs Handbook
- Vaillant UK - Why is my boiler losing pressure?
- Consumer Council for Water (CCW) - What can I do if I suspect there is a leak on my private water supply?
- Drinking Water Inspectorate - Water storage tanks and cisterns
- Association of Plumbing & Heating Contractors (APHC) - Dealing with plumbing and heating emergencies
What does a published pipe-repair price include?
The example below covers an easily accessible burst pipe dealt with as an emergency, where the supply can be isolated. Which? estimates 1 - 2 hours for that job. The survey was gathered in November 2025; we checked the published page on 29 September 2026. A small drip, waste-pipe fault, heating leak or concealed pipe needs its own quote.
Which? surveyed accessible burst-pipe job
UK survey; Which? says prices may be toward upper end in London/South East · job · VAT excluded
Ask for the full scope
Ask whether the quote includes diagnosis, emergency attendance, labour, parts and VAT, and whether opening or making good a wall, floor or ceiling is extra. The price should describe the actual pipe and access conditions.
What should you tell a plumber or landlord?
Where did water first appear?
Name the visible pipe/body, connection or valve if known; say “unsure” if it could have travelled from above or behind a surface.
What was already in use?
Say whether the leak was noticed while a fixture was idle, after ordinary drainage, or around radiator/heating pipework. Do not recreate the leak.
How urgent is it?
Describe whether the water is actively flowing, spreading, pooling or near electrics. Mention if a known private inside stop tap was safely closed and whether water continued.
What do you know about access?
Share a dry-position photo and any visible pipe, boiler or appliance model only if already available. Do not remove panels or move connected appliances to obtain it.
Helpful tools: Plumber visit checklist. Use these with the guidance above.
Sources
- WaterSafe Register - What should I do if a water pipe bursts?
- Thames Water Utilities Limited - Find and use your inside stop valve
- WaterSafe Register - What to do with a leak under your sink
- Hightown Housing Association - Repairs Handbook
- Electrical Safety First - Electrical safety after a flood
- Vaillant UK - Why is my boiler losing pressure?
- Drinking Water Inspectorate - Water storage tanks and cisterns
- Association of Plumbing & Heating Contractors (APHC) - Dealing with plumbing and heating emergencies
Common questions about leaking pipes
Will the stop tap stop every leak?
No. A known private inside stop tap may limit incoming mains water. Stored hot water, a waste pipe or a separate heating circuit may continue, so do not operate other valves if you are unsure.
How can I tell supply water from a waste leak?
Use timing you already noticed during ordinary use. A supply-side leak may be visible while a fixture is idle; a waste leak may appear during or after drainage. Neither clue proves the source; do not run water to test it.
Could a falling boiler pressure mean a pipe leak?
It can be a clue on a sealed heating system, but it does not locate a leak and pressure can fall for other reasons. Do not top up as a substitute for investigation; contact a heating engineer.
What if water comes through a ceiling or wall?
That is a hidden-leak situation outside this guide’s visible-pipe scope. Keep clear if water is spreading or near electrics, and contact the landlord/building manager or an appropriate plumber promptly.
What does the burst-pipe price mean?
Which?’s £100 - £500 figure assumes an easily accessible burst water pipe, an emergency call-out and an isolatable supply; its note includes call-out, labour and materials but excludes VAT. It is not a price for every leak.
Sources
- WaterSafe Register - What should I do if a water pipe bursts?
- Thames Water Utilities Limited - Find and use your inside stop valve
- WaterSafe Register - What to do with a leak under your sink
- Hightown Housing Association - Repairs Handbook
- Electrical Safety First - Electrical safety after a flood
- Vaillant UK - Why is my boiler losing pressure?
- Which? - How much do plumbers cost?
- Drinking Water Inspectorate - Water storage tanks and cisterns
- Association of Plumbing & Heating Contractors (APHC) - Dealing with plumbing and heating emergencies
EVIDENCE & ACCOUNTABILITY
Sources and review
Prepared by Plumber.org.uk with AI assistance, using the sources listed below. These sources support the explanations; they do not endorse this website.
Source-checked guide with independent editorial review and AI-assisted research. No professional plumbing review is claimed. Initial research: 2026-09-29. Updated: 2026-09-30. This is general information, not an assessment of your installation. Prices can change; confirm compatibility and the full repair quote before buying or booking.
How we research and update guides. Spotted an error? Contact us with the page address and the detail to check. This form is for general enquiries and editorial feedback, not emergency assistance.
- WaterSafe Register - What should I do if a water pipe bursts?
Current consumer guidance: locate and close the internal stopcock; switch off central heating/boiler for a burst; catch escaping water with towels or buckets; contact a WaterSafe-recognised plumber; if water has reached electrics, switch off electricity at the mains first. This guide adopts only safe, dry-position damage limitation and the bounded known-stop-tap action; it does not reproduce drainage or electrical isolation instructions.
- Thames Water Utilities Limited - Find and use your inside stop valve
Sections “Flats and shared water supply” and “How to use your inside stop valve”: shared valves may exist; a conventional valve closes clockwise; do not use excessive force; water may take a few minutes to stop running from taps; contact a plumber if finding/using the valve is a problem.
- WaterSafe Register - What to do with a leak under your sink
Previously checked 28 Sep 2026. Sections “Is a leak under the sink an emergency?” and “How to find where the leak is coming from”: note source and damage, take photos, catch water in a bucket only when safe, view from a safe position, look directly above, and possible supply fittings/waste pipes. Advises a qualified plumber rather than a guessed repair. Reused only for safe observations, water travel and named under-sink overlap. Root rechecked 2026-09-29, Reasons you have a leak under the sink: worn washers, perished seals, loose fittings, knocks and cracked/slipped plastic waste pipes.
- Hightown Housing Association - Repairs Handbook
Previously checked 28 Sep 2026. PDF page 10, “Water leaks”, lines 492 - 505 asks tenants to distinguish supply from waste pipe and report hot/cold supply/electrical impact. Page 12, “Baths”, lines 554 - 573 contrasts a bath waste-pipe leak noticed during emptying with a supply leak described as constant; page 12 lines 577 - 600 notes sinks/basins have traps and asks residents to report location. Used only as a qualified route/timing clue, not a test.
- Electrical Safety First - Electrical safety after a flood
Previously checked 28 Sep 2026: keep clear of exposed wiring and water-damaged electrical equipment; have affected equipment checked by an electrician.
- Vaillant UK - Why is my boiler losing pressure?
Current page sections “What causes a boiler to lose pressure?” and “How do I find a leak in my heating system?”: system/radiator leaks can lower pressure; damp around radiator connections and discoloured paint/flaking at pipework/skirting can be clues; condensation can also wet pipework; do not repair loose/broken joints unless trained; arrange a specialist. Root rechecked 2026-09-29, causes and leak-finding sections: corrosion or loosening in heating circuit; condensation can wet pipework without a leak.
- Consumer Council for Water (CCW) - What can I do if I suspect there is a leak on my private water supply?
Current FAQ: responsibility depends on location; customer supply pipe runs from house to property boundary; water company maintains water main and communication pipe. It says domestic customers should ask their water company whether one-off leak-location/repair assistance is available because policies vary.
- Which? - How much do plumbers cost?
Section “How much does it cost to fix burst pipes and replace water tanks?” row “Fix burst water pipe”: £100 - £500, 1 - 2 hours; assumes easily accessible pipes, emergency call-out and isolatable supply; includes call-out, labour and materials. Following note: 25 Which? Trusted Traders surveyed November 2025; prices include labour and materials but exclude VAT unless stated and may be towards upper end in London/South East.
- Drinking Water Inspectorate - Water storage tanks and cisterns
Previously checked 28 Sep 2026. “Do I have a water storage tank?”: some older properties have tank-fed cold taps, while newer homes, especially with unvented systems, are likely to have direct mains-fed hot and cold taps. Reused to qualify that household supplies vary.
- Association of Plumbing & Heating Contractors (APHC) - Dealing with plumbing and heating emergencies
Previously checked 28 Sep 2026. PDF pages 1 - 2 distinguish appliance isolation valves from main isolation and discuss separate hot-water-cylinder supply. Reused only to avoid implying that one mains stop tap isolates every system.