A practical UK guide for London homeowners, landlords, and tenants on finding the internal stop tap (also called stopcock or stop valve), understanding the responsibility split with Thames Water, and knowing what to do — and what not to do — when you need to turn off your water in a hurry.

This guide is based on Thames Water’s published Customer Side Leakage Code of Practice and consumer guidance, the Water Industry Act 1991 (which applies in England and Wales), the Water Supply (Water Fittings) Regulations 1999, the Water Supply (Water Quality) Regulations 2016, the Landlord and Tenant Act 1985, the Housing Act 2004, the Homes (Fitness for Human Habitation) Act 2018, Drinking Water Inspectorate guidance, HSE guidance, and Gas Safe Register guidance. Much of London is served by Thames Water, with parts of outer London served by Affinity Water, SES Water, or Essex & Suffolk Water — the responsibility framework described in this guide is broadly the same across English and Welsh water undertakers under the Water Industry Act 1991, but practical contact routes and Code of Practice details differ by supplier.

---

⏱️ Quick answer

In London homes, the first place to check is under the kitchen sink, where the cold mains pipe enters the property.¹ ²⁰ If it is not there, check the downstairs WC, utility cupboard, under the stairs, near the front door, or service cupboard. Turn clockwise until resistance is met; do not overtighten. If it will not turn, do not force it — call your water company’s emergency line (numbers in the safety note below) or see section 5 for guidance on the outside stop valve.

---

⚠️ Quick safety note

If water is actively flooding your property:

1. If it is safe and you can reach the consumer unit (fuse box) without entering water or touching wet electrical equipment, switch off the supply. Never touch the consumer unit if you are standing in water. If you are unsure, do not re-enter the flooded area until power has been isolated by a competent person.²
2. Try the internal stop tap. Use the external stop tap (OSV) at the property boundary only in an emergency, and only if you have access, the right tool, and you are confident the OSV serves only your property — see section 5.
3. Call your water company’s emergency line:
   • Thames Water (much of London): 0800 316 9800 (24/7)³
   • Affinity Water (parts of north-west London): emergencies and burst mains 0345 357 2407 (24/7); leak reporting freephone 0800 376 5325
   • SES Water (parts of south London / Surrey): 01737 772000 (24/7)
   • Essex & Suffolk Water (parts of east London): heavy leak / burst 0800 526 337 (24/7); no water 0345 782 0999
4. If you smell gas or suspect a gas leak, call 0800 111 999 (free, 24/7).⁴
5. Call 999 only where there is immediate danger to life — for example, fire or electrocution risk.⁵

If you are unsure who supplies your address, check your bill or use your water company’s postcode checker. Emergency numbers verified April 2026 — please reverify with the relevant water company before publication.

Do not force a stop tap that will not turn — overforcing can shear the spindle or crack the body and convert a working tap into an active leak. See section 7.

---

Contents

1. TL;DR — How to find your stop tap
2. Stop tap, stopcock, stop valve — what these terms mean
3. Where the stopcock is in a UK home — typical locations
4. How to operate the internal stop tap correctly
5. The external stop tap (OSV) at the property boundary
6. Who’s responsible for what — the Thames Water responsibility split
7. If your stop tap is seized, stuck, or won’t turn
8. Lead pipes in older London homes
9. Tenants and landlords — who does what
10. What we can’t advise without a site visit
11. How to find a qualified plumber
12. FAQs
13. Sources

---

1. TL;DR — How to find your stop tap

If you need to turn off your water now:

1. Most likely location: under the kitchen sink. Thames Water’s published Code of Practice describes the internal stop valve as “usually under your kitchen sink”,¹ and Thames Water’s consumer guidance states that “inside stop valves are usually located just after the water pipe enters the house”.²⁰ Open the cupboard and look for a vertical pipe with a T-shaped handle or red lever where the cold mains water enters the property.
2. If not under the kitchen sink, typical alternative locations include the downstairs WC, utility room, behind the washing machine, under the stairs, near the gas/electric meters, in the hallway, or in a service cupboard near the front door of a flat. These are typical patterns, not guaranteed.
3. Turn it clockwise until resistance is met. Do not overtighten.
4. If it won’t turn easily, stop. Don’t force it. See section 7.
5. If you can’t find it inside, the external stop tap (OSV) at the property boundary is your fallback — but Thames Water states the OSV “should only be used in an emergency”.¹⁶ See section 5.

If water is actively flooding and you cannot stop it within a few minutes, call your water company’s emergency line (numbers in the safety note above).

---

2. Stop tap, stopcock, stop valve — what these terms mean

The terms stop tap, stopcock, and stop valve are used interchangeably in UK plumbing, including in Thames Water’s own Customer Side Leakage Code of Practice, which uses “stoptap”, “stopcock”, and “stop valve” within the same document.⁶

There are three you should know about in a typical London home:

Internal stop valve (ISV). The valve inside your property where the cold mains water enters the house. Thames Water’s Customer Side Leakage Code of Practice describes the ISV as “usually under your kitchen sink”.¹ Thames Water’s consumer guidance adds that “inside stop valves are usually located just after the water pipe enters the house” and that there may be a communal ISV where supply is shared, plus an additional ISV where the supply enters a flat.²⁰

External stop tap (OSV) — also called the outside stop valve or external stopcock. Thames Water’s Code of Practice describes external stoptaps as “apparatus belonging to us which are installed on each service pipe to control the water flow using a valve mechanism.”⁶ They are usually installed in the public footpath at or near the property boundary, but may be installed in private premises such as a garden or driveway.⁶ The OSV is for emergency use only — see section 5.

Service / appliance isolators. Small mini-valves on individual appliances (washing machine, dishwasher, toilet cistern, individual taps), usually with a slotted head that turns a quarter-turn with a flat-blade screwdriver. These let you isolate a single appliance without shutting off the whole house. They are not the same as the main stop tap.

In an emergency, the internal stop valve is the one you want.

---

3. Where the stopcock is in a UK home — typical locations

Thames Water’s Customer Side Leakage Code of Practice describes the internal stop valve as “usually under your kitchen sink”.¹ Thames Water’s consumer guidance adds that “inside stop valves are usually located just after the water pipe enters the house”.²⁰ This is the most commonly advised first place to check, because the cold mains water often enters near the kitchen or another ground-floor service point.

The locations below are typical patterns observed across UK property types, not guarantees. A property that has been renovated may have the stop tap in a non-standard position, often left in the original location even after the kitchen has been moved. If your stop tap is not in any of the typical locations, follow the cold mains pipe back from the kitchen tap to where it enters the building — the stop valve should be on that pipe if one has been fitted.

Where to look first

In order of typical likelihood:

1. Under the kitchen sink (the cold mains entry point in most properties).¹
2. Downstairs WC, utility room, or behind the washing machine (alternative cold-mains entry points).
3. Under the stairs, in the hallway, or near the gas and electric meters (where a service riser is grouped near the front of the property).
4. In an airing or service cupboard (more common in flats and post-war properties with the cold mains feeding a hot water cylinder).
5. Near the front door of a flat, in a service cupboard with the boiler and consumer unit.

General locating tips

• Look for the cold mains pipe — typically 15mm or 22mm copper (or, in older properties, lead — see section 8), running upwards from below floor level. The stop valve sits on this pipe.
• Follow the cold mains backwards from the kitchen tap to where it enters the property.
• If the kitchen has been renovated, the stop tap may have been left in the original location even if the sink has been moved.
• If you know where the external stop tap (OSV) is, the internal one is generally in line with it on the inside of the wall, since the supply pipe runs in a roughly straight line from boundary to building entry.
• Check the original property plans if you have them — building plans may mark stop valve positions.

Flats, leaseholds, and managing-agent-controlled valves

In London flats and leasehold buildings, the picture can be more complex:

• Purpose-built flats and mansion blocks may have a building-wide cold mains stop valve in a communal service riser cupboard, controlled by the freeholder or managing agent. Each individual flat then has its own stop valve where the supply enters the flat.²⁰ In an emergency, your individual flat’s valve should be sufficient — but if it is not accessible, your managing agent or block freeholder should be your first call.
• Converted Victorian or Edwardian houses divided into flats sometimes share a single original whole-house stop valve. Each flat then ideally has its own additional stop valve, but this is not always the case.
• Tenants in leasehold flats: if the stop valve serving your flat is in a communal area you do not have access to, raise this with your managing agent or freeholder. It is good practice for building water-shut-off arrangements to be communicated to leaseholders and tenants, and access arrangements to communal valves should be confirmed at move-in or purchase.

If you cannot find an internal stop valve, you may not have one — this is observed in older installations that were supplied without an internal stop valve, relying on the OSV. Fitting an internal stop valve is strongly recommended good practice; this is plumber work and not a DIY task on a live mains supply.

---

4. How to operate the internal stop tap correctly

Before you need it in an emergency, find your stop tap, check it works, and make sure you can reach it. A stop tap that has not been turned for a long time may have seized, and the moment of a burst pipe is not the moment to discover that.

Work on mains-connected pipework must comply with the Water Supply (Water Fittings) Regulations 1999; non-compliant work can lead to enforcement action by the water undertaker.⁸

To turn the water off

1. Locate the stop tap.
2. Turn the handle clockwise until resistance is met. Do not overtighten. Thames Water’s consumer guidance notes that “you shouldn’t need to use excessive force to turn it further”.²⁰ Older valves may vary in feel and resistance; quarter-turn lever handles need a quarter-turn, while T-bar handles typically need several full turns.
3. Run a cold tap somewhere in the house to confirm the supply has stopped. The flow should slow to a trickle within seconds and then stop.
4. Hot taps may continue to flow briefly because of stored water, residual pressure, or the type of hot-water system fitted. That’s normal.

To turn the water back on

1. Turn the handle anti-clockwise until fully open, then turn back a quarter-turn. Leaving it fully open at the stop can make it harder to free on the next attempt.
2. Check for visible leaks at the stop tap and along visible pipework. A new leak at the spindle after closing and reopening should prompt a plumber visit.
3. Run cold taps briefly at the kitchen and bathroom to clear any air in the line.

Test it occasionally

Testing the internal stop tap from time to time — close, run a tap to confirm, reopen — is good maintenance practice that helps the spindle and packing stay free. If the tap turns but the water doesn’t stop, the internal washer or jumper has likely failed and the tap needs replacing. This is a job for a plumber, not a DIY task on a live mains supply.

---

5. The external stop tap (OSV) at the property boundary

Thames Water’s published consumer guidance is explicit that the OSV is for emergency use only: “You should only use your outside stop valve in an emergency, for example if you have a leak on the supply pipe between the inside and outside stop valves.”¹⁶ Thames Water also states: “To protect your home, you should always have a working inside stop valve. Use this as the main way to turn your water on and off.”¹⁶

Thames Water’s Customer Side Leakage Code of Practice describes external stoptaps as “apparatus belonging to us which are installed on each service pipe to control the water flow using a valve mechanism. Stoptaps are usually installed on the service pipe in the footpath, however they may be installed in private premises, such as a garden or driveway.”⁶ The Code of Practice also confirms that “we have a legal power to fit a stoptap to any service pipe (including a supply pipe) at our expense.”⁶

How to find it

• Look in the footpath directly outside your property, generally close to the boundary line.
• It’s typically housed in a small round (about 100mm) or square (about 150mm) plastic or metal cover, often with “WATER”, “W”, or “STOP TAP” embossed on it.
• A water meter, where fitted, is usually (but not always) in the same location as the OSV. Thames Water’s Code of Practice specifies that “the position of the meter does not determine pipe ownership or responsibility.”⁶ The meter is Thames Water’s apparatus regardless of its location.

Operating the OSV

The OSV usually requires a stop tap key — a long T-shaped tool that reaches down into the chamber and engages the spindle. Standard household stop tap keys are sold at hardware stores and DIY retailers. Use the correct stop tap key; avoid improvised tools. Pliers, mole grips, or adjustable spanners can shear the spindle off and convert the OSV into a leaking, unrepairable fitting.

When you should not operate the OSV yourself

If there is any uncertainty about ownership, shared supply, or condition, do not operate the OSV — contact the water company. Even in an emergency, OSV use by customers is not always safe or appropriate. Contact your water company for isolation in any of these situations:

• You are not certain the OSV serves only your property. In some terraced streets, particularly older ones, a single OSV serves more than one property. Operating it will shut off your neighbours’ water without warning.
• The chamber is flooded, full of debris, or you cannot see the spindle clearly.
• You don’t have the correct stop tap key.
• The OSV is on a shared supply. Where a shared supply exists, the responsibility for maintaining the shared section is joint between the property owners served by the pipe.⁶

**Do not attempt to repair or dismantle the OSV. It is Thames Water apparatus; contact Thames Water if it is damaged, inaccessible, or inoperable.**⁶

If the OSV is broken

The OSV is Thames Water’s apparatus and Thames Water is responsible for maintaining it. Thames Water can advise on OSV repair or access where isolation is needed.

If you need the OSV repaired so a plumber can work on your internal stop tap, your most effective route is:

1. Contact Thames Water and explicitly state that you need the supply isolated to carry out essential plumbing work on your internal pipework.
2. If Thames Water cannot attend in a reasonable timeframe, a competent plumber may be able to use a pipe freezing kit to temporarily isolate the supply pipe so the internal stop tap can be replaced — see section 7 for important caveats on pipe freezing.

A persistently broken OSV is not a reason to attempt repair yourself. Contact Thames Water and let their operative handle it.

---

6. Who’s responsible for what — the Thames Water responsibility split

The general framework for who owns and is responsible for which section of water pipe is set by the Water Industry Act 1991 (England and Wales)⁷ and is detailed in each water company’s published Codes of Practice. For most London properties, Thames Water’s Customer Side Leakage Code of Practice is the authoritative reference.

The responsibility split generally runs along the property boundary, with some specific exceptions covered below.

Thames Water’s responsibility

Thames Water’s Code of Practice states: “We’re responsible for the mains that carry water around the region, and for the ‘communication pipe’ – the one linking your water supply pipe to our water main. It’s our responsibility to maintain and repair our water mains and communication pipes.”⁹

This includes:

• The water main running along the public highway.
• The communication pipe running from the water main to the boundary of your property.
• The external stop tap (OSV), where one is fitted on the communication pipe (Thames Water’s apparatus).⁶
• The water meter, where fitted (the meter is Thames Water’s apparatus regardless of location).⁶

Customer’s responsibility

Thames Water’s Code of Practice states: “Generally, the water supply pipe that runs from the boundary of your property into your home is your responsibility, along with any internal pipes and fittings.”⁹

This includes:

• The supply pipe running from your property boundary to the internal stop tap inside the house. The Code of Practice clarifies that “if your supply pipe crosses land belonging to someone else… you’re responsible for the pipe up to the point that it connects to our communication pipe.”⁹
• The internal stop valve (ISV) itself.
• All internal pipework, fittings, and appliances — toilets, taps, showers, water tanks, washing machines.

If a leak is found on your supply pipe

Thames Water’s Code of Practice specifies: “You need to get your leak fixed within four weeks of us confirming it.”¹⁰ This is an obligation under Thames Water’s Code of Practice and the water company’s enforcement powers under the Water Industry Act 1991, not primary statutory legislation; other water companies in England and Wales have similar Codes that may differ in detail.⁷ ¹⁰

If you have a meter, you are also liable for the metered cost of all water lost through the leak.¹⁰ Thames Water may offer a leakage allowance under defined conditions to credit your account for water lost during a confirmed leak, subject to eligibility criteria in the Code of Practice.¹⁰

Shared supplies

Thames Water’s Code of Practice acknowledges that “sometimes a single supply pipe serves two or more properties — a ‘shared supply’… This is more common when buildings are close together, in a side-by-side layout, such as on a terraced street. It means you are responsible for maintaining the part of the pipe which supplies only your property, and you and your neighbours have joint responsibility for maintaining the shared part of the pipe.”⁶

Resolving leaks on shared supply pipes can be complex, particularly when neighbours are uncontactable or unwilling to contribute.

---

7. If your stop tap is seized, stuck, or won’t turn

A stop tap that hasn’t been turned for a long time can seize.

Do not force a seized stop tap

If the handle won’t turn with reasonable effort by hand:

• Stop. Do not extend the handle with a wrench, mole grips, or spanner.
• Do not strike the body of the tap to free it.
• Do not heat the tap with a blowtorch or heat gun.

Forcing a seized tap can shear the spindle off, crack the brass body, or cause the gland packing to fail — converting a working tap into an active leak that you can no longer stop. In the worst case, this means an internal flood with no way to isolate the supply except via the external stop tap.

What to do instead

1. If you have a suspected leak that needs the supply off urgently, use the external stop tap (OSV) — see section 5 — or call your water company’s emergency line.
2. If the issue is non-urgent, book a plumber to replace or repair the stop tap.

If your stop tap is seized, leaking, or inaccessible, find a plumber via section 11. Verify their credentials before booking — see that section for the official routes.

Replacing a seized stop tap

This is not a DIY task on the live mains supply of a property. It requires either operating the OSV (which may be problematic on shared supplies) or using a pipe freezing kit.

Pipe freezing — important caveats

Pipe freezing is a specialist technique used by competent plumbers to temporarily freeze a section of supply pipe so a downstream component can be replaced without operating the OSV. Thames Water’s consumer guidance acknowledges that “an accredited plumber can use freezing and clamping as a short-term solution”.²⁰

As competent plumbing practice, pipe freezing must not be attempted by homeowners. It should only be carried out by a competent plumber with suitable equipment. Failure of the ice plug can cause uncontrolled mains-pressure flooding.

It is not a routine alternative to OSV operation, and it is not always suitable. The following considerations reflect competent plumber judgement rather than manufacturer specification:

• It is not suitable for degraded or perished pipework, where freezing can split the pipe.
• It is not suitable for some lead installations, where the freeze stress can damage soft lead pipe.
• It is not suitable in high-flow mains conditions, where the flow rate prevents the ice plug forming.
• It is a paid service with its own equipment requirements.

Use a plumber. Verify them via the routes in section 11.

Service isolators as a partial backup

Modern installations often include a service isolator (a small inline mini-valve) immediately downstream of the main stop tap, providing a backup if the main tap fails. Older properties typically do not have this. Adding one is a legitimate option to discuss with your plumber when you next have plumbing work done.

---

8. Lead pipes in older London homes

The Drinking Water Inspectorate’s consumer guidance states that “before 1970, lead pipework was commonly used to connect properties to the mains water network.”¹¹ Lead is no longer permitted in new drinking-water installations under current regulations, but the DWI confirms that “many older properties that have not been modernised are likely to have lead pipework underground and/or inside the building.”¹¹ Existing lead pipework is not in itself unlawful, and many older London properties retain it.

If you suspect lead pipework, the practical hierarchy of action is: identify (visual inspection or plumber’s confirmation), test (request a water sample test from your water company or local authority if you are concerned about exposure), replace (work with a competent plumber and your water company on a coordinated supply-pipe replacement).

The UK lead standard

The UK regulatory standard for lead in drinking water is 10 micrograms per litre (µg/L), set under the Water Supply (Water Quality) Regulations 2016, with the point of compliance at the consumer’s tap.¹² The Drinking Water Inspectorate notes that “lead can build up in the body and it is recommended that exposure to lead be minimised as far as possible.”¹¹

Identifying lead pipework

• Lead pipework is identifiable by its dull grey appearance and the fact that it can be marked with a fingernail.
• Copper pipework is typically a dull pink-orange (or green from oxidation).
• Modern blue plastic MDPE is unmistakable.

Lead replacement schemes

The Drinking Water Inspectorate confirms that water companies “are legally required to replace their communication pipe, if it is made of lead and is at risk of contributing to the amount of lead in the drinking water supply.”¹¹ Thames Water and other UK water companies operate lead replacement schemes that may cover the cost of replacing the communication pipe (the water company’s section) when the customer arranges replacement of the supply pipe (the customer’s section). Contact Thames Water directly for current scheme conditions.

DWI consumer flushing advice for homes with lead pipework

The Drinking Water Inspectorate’s published consumer advice for homes with lead pipework is: “For drinking and cooking, run the tap to clear any water that has been standing in the pipework for [a] while, for example, overnight. A washing up bowl full is normally enough to clear the pipe of standing water.”¹¹ The DWI also advises flushing the tap well for at least 10 minutes after any work has been carried out on a lead pipe.¹¹

If you discover that your incoming pipe and stop tap connection are on lead, this is a good moment to speak to a plumber about a supply-pipe replacement and to contact Thames Water about its lead replacement scheme.

---

9. Tenants and landlords — who does what

For privately rented properties, Section 11 of the Landlord and Tenant Act 1985 places repair duties on the landlord for the structure and exterior of the property and for installations including the supply of water.¹³

If you are a tenant

• You should know where your internal stop tap is — ask your landlord or letting agent at the start of the tenancy if the location is not obvious. This is a reasonable request.
• A non-functioning, seized, or inaccessible stop tap is a repair issue under Section 11 and should be reported to your landlord or letting agent, ideally in writing for your records.
• In a leak emergency, turn off the supply at the internal stop tap if you can, or at the OSV outside if you cannot and it is safe to do so. Then notify your landlord or letting agent immediately.
• Do not commission third-party plumbing work to replace a seized stop tap unless your landlord explicitly authorises it. Tenants who arrange unauthorised repair work may not be reimbursed.

Reasonable time for repair

Section 11 requires landlords to carry out repairs within a reasonable time after notice. What is reasonable depends on the facts, including the severity and risk.¹³ A seized or inaccessible stop tap that prevents emergency isolation in a leak is a more urgent matter than a minor cosmetic plumbing issue. Where landlords delay urgent repairs unreasonably, tenants have additional rights under the Homes (Fitness for Human Habitation) Act 2018.¹⁴

Escalation route if a landlord won’t act

If you have reported a seized or inaccessible stop tap in writing and your landlord has not arranged repair within a reasonable time, you can escalate to your local authority’s Environmental Health team. Local authorities have powers under the Housing Act 2004 to inspect rented properties and require landlords to remedy hazards.¹⁷ You can ask the local authority to assess whether the issue forms part of a wider housing hazard under the Housing Health and Safety Rating System.¹⁸

If you are a landlord

• The internal stop tap is part of the water-supply installation you are responsible for under Section 11.¹³
• A seized or inaccessible stop tap is a repair priority — if it fails when needed, a small leak can become a major water-damage claim.
• Periodic testing of the stop tap during inspections, and making its location clear to tenants at the start of each tenancy, is good practice.
• For HMOs and licensable properties, your local authority’s licensing conditions may include specific requirements about access to safety-critical infrastructure, including water shut-off.

If you are a council or housing-association tenant

• The internal stop tap is the council’s or housing association’s responsibility as part of property maintenance.
• Report stop tap problems through your landlord’s repair line — contact details are on your tenancy agreement, the landlord’s website, or your most recent rent statement.
• For repairs the landlord is slow to action, tenants have rights under Section 11 and the Homes (Fitness for Human Habitation) Act 2018¹⁴ — but the first step is always to log the repair through the official channel.

---

10. What we can’t advise without a site visit

This guide explains the general framework for finding and operating a stop tap in a London home. It cannot substitute for a plumber’s site visit, which is the only way to:

• Confirm the exact location of your internal stop tap if it isn’t in the typical places.
• Identify lead pipework reliably and assess whether replacement is appropriate.
• Diagnose why a stop tap is seized, leaking, or unable to fully shut off the supply.
• Replace a seized or failed stop tap safely.
• Investigate a confirmed supply-pipe leak.
• Confirm whether your supply is shared with a neighbour, and where the boundary lies.

This guide also cannot tell you:

• The specific layout of pipework in your property.
• Whether your particular property’s OSV is solely yours or shared.
• The exact age and material of your supply pipe without a physical inspection.

For any plumbing issue beyond locating and operating an existing, functional stop tap, book a plumber.

---

11. How to find a qualified plumber

Plumbing water-supply work in England and Wales does not have a single statutory register equivalent to Gas Safe. It is governed by the Water Supply (Water Fittings) Regulations 1999, which set out the legal requirements for fittings, materials, and workmanship for any installation connected to the public water supply.⁸ Work done in breach of these Regulations can be the subject of enforcement action by the water company.

The WaterSafe Register scheme

WaterSafe Register (described by the scheme itself as the UK’s national register of approved plumbing installers, formerly WaterSafe and rebranded 1 April 2026) lists plumbers who have been approved by their Approved Contractors’ Scheme — including WIAPS (Water Industry Approved Plumbing Scheme), CIPHE, APHC, and SNIPEF — as competent to install in compliance with the Water Supply (Water Fittings) Regulations 1999.²¹ ¹⁵ According to WaterSafe Register’s own publications, the scheme is supported by UK water companies and backed by drinking water regulators in England, Wales, Scotland and Northern Ireland.²¹ Thames Water — the water company for much of London — independently directs customers to WaterSafe Register-approved contractors via its Find a plumber page.²²

Use it to:

• Find an approved plumber by postcode.
• Check whether a specific plumber is on the scheme.
• Confirm that work on cold mains pipework will be done in compliance with water regulations.

WaterSafe Register is not a regulator, and accreditation is voluntary. A plumber not on the scheme is not necessarily incompetent — but using a WaterSafe Register-approved plumber gives you evidence that the installer was listed on an approved-contractor route at the time of booking.

Thames Water’s recommended route

Thames Water closed its own Approved Contractors Scheme (TAPS) in October 2022 and joined WIAPS.¹⁹ Thames Water’s current Find a plumber guidance directs customers to choose a WaterSafe Register-approved contractor recognised by water company schemes including WIAPS.²²

Trade bodies

Several professional trade bodies operate plumber-membership schemes that include competence standards:

• CIPHE (Chartered Institute of Plumbing and Heating Engineering) — chartered professional body
• APHC (Association of Plumbing and Heating Contractors) — UK trade body
• SNIPEF (Scotland and Northern Ireland Plumbing Employers’ Federation) — Scotland and Northern Ireland trade body
• WIAPS (Water Industry Approved Plumbing Scheme) — managed by Water Regs UK on behalf of the majority of water undertakers in England and Wales

Membership of these bodies is voluntary but is one signal of competence and accountability.

---

Verification and commercial disclosure

Use the official scheme registers where applicable: Gas Safe for gas work (statutory) and WaterSafe Register as a recognised approved-plumber route for water work. Verify any plumber’s credentials directly via these schemes before booking and before work starts.

The line below describes a commercial directory operated by VerifiedPlumbers and is not endorsed by any regulator. Verification of any individual plumber listed on it should be done via the official scheme registers above.

About the VerifiedPlumbers London directory

VerifiedPlumbers is a commercial directory of London plumbers and gas engineers. For the directory, see VerifiedPlumbers — London.

Get quotes

For non-emergency work — replacing a seized stop tap, fitting a service isolator, replacing a lead supply pipe — get 2–3 quotes from approved plumbers before agreeing to the work. Ask each to specify whether the cost includes operating the OSV, pipe freezing, or any reinstatement work.

---

12. FAQs

---

13. Sources

¹ Thames Water — Customer Side Leakage (CSL) Code of Practice (specifies internal stop valve “usually under your kitchen sink” in the leak-detection guidance). https://www.thameswater.co.uk/media-library/home/about-us/governance/our-policies/codes-of-practice/leakage-code-of-practice.pdf

² HSE — Electricity at work (broad authority for electrical safety; specific domestic flood instructions in this guide are general safety advice). https://www.hse.gov.uk/electricity/

³ Thames Water — leakline / supply pipe leak contact (0800 316 9800, 24/7). Cited in Thames Water Customer Side Leakage Code of Practice. https://www.thameswater.co.uk/media-library/home/about-us/governance/our-policies/codes-of-practice/leakage-code-of-practice.pdf

⁴ Gas Safe Register — gas emergency contacts (0800 111 999 for England, Wales, and Scotland; free, 24/7). https://www.gassaferegister.co.uk/contact-us/

⁵ GOV.UK — When to call 999. https://www.gov.uk/contact-emergency-services

⁶ Thames Water — Customer Side Leakage Code of Practice (external stoptap as Thames Water apparatus; “stoptap” / “stopcock” / “stop valve” used interchangeably; meter ownership; legal power to fit a stoptap; shared supply framework). https://www.thameswater.co.uk/media-library/home/about-us/governance/our-policies/codes-of-practice/leakage-code-of-practice.pdf

⁷ Water Industry Act 1991 (England and Wales) — legislation.gov.uk. https://www.legislation.gov.uk/ukpga/1991/56/contents

⁸ Water Supply (Water Fittings) Regulations 1999 — legislation.gov.uk. https://www.legislation.gov.uk/uksi/1999/1148/contents/made

⁹ Thames Water — Customer Side Leakage Code of Practice (Thames Water responsibility for mains and communication pipes; customer responsibility for supply pipe and internal pipework; supply-pipe-crossing-other-land scenario). https://www.thameswater.co.uk/media-library/home/about-us/governance/our-policies/codes-of-practice/leakage-code-of-practice.pdf

¹⁰ Thames Water — Customer Side Leakage Code of Practice (four-week repair obligation; metered liability for leakage; leak allowance framework). https://www.thameswater.co.uk/media-library/home/about-us/governance/our-policies/codes-of-practice/leakage-code-of-practice.pdf

¹¹ Drinking Water Inspectorate — Lead in Drinking Water (consumer guidance: lead pipework banned from new use; “lead can build up in the body and it is recommended that exposure to lead be minimised as far as possible”; flushing advice for homes with lead pipework; water companies’ communication-pipe replacement obligation where pipe is at risk of contributing to lead). https://www.dwi.gov.uk/lead-in-drinking-water/

¹² Water Supply (Water Quality) Regulations 2016 — legislation.gov.uk; UK lead standard 10 µg/L at consumer tap. https://www.legislation.gov.uk/uksi/2016/614/contents/made

¹³ Landlord and Tenant Act 1985, Section 11 — legislation.gov.uk. https://www.legislation.gov.uk/ukpga/1985/70/section/11

¹⁴ Homes (Fitness for Human Habitation) Act 2018 — legislation.gov.uk. https://www.legislation.gov.uk/ukpga/2018/34

¹⁵ WaterSafe Register — UK national register of approved plumbing installers (voluntary, industry-backed; Approved Contractors’ Schemes: WIAPS, CIPHE, APHC, SNIPEF). https://www.watersafe.org.uk/

¹⁶ Thames Water — How to find and use your outside stop valve (consumer guidance: “You should only use your outside stop valve in an emergency”; ISV as primary route). https://www.thameswater.co.uk/help/water-and-waste-help/how-to-turn-your-water-on-and-off/how-to-find-and-use-your-outside-stop-valve

¹⁷ Housing Act 2004 — legislation.gov.uk (local authority inspection and enforcement powers in respect of residential premises). https://www.legislation.gov.uk/ukpga/2004/34/contents

¹⁸ GOV.UK — Housing Health and Safety Rating System (HHSRS) operating guidance. https://www.gov.uk/government/publications/housing-health-and-safety-rating-system-guidance-for-landlords-and-property-related-professionals

¹⁹ WaterSafe Register — History of WaterSafe Register (timeline confirms Thames Water closed its Approved Contractors Scheme in October 2022 and joined WIAPS; WaterSafe rebranded to WaterSafe Register in April 2026). https://www.watersafe.org.uk/about/10-years-of-qualified-approved-water-contractors/

²⁰ Thames Water — How to find and use your inside stop valve (consumer guidance: ISV “usually located just after the water pipe enters the house”; communal ISV for shared supplies; additional ISV where supply enters a flat; turn instruction “you shouldn’t need to use excessive force”; pipe freezing acknowledged as accredited-plumber technique). https://www.thameswater.co.uk/help/water-and-waste-help/how-to-turn-your-water-on-and-off/how-to-find-and-use-your-inside-stop-valve

²¹ WaterSafe Register — Plumber register gets new name (1 April 2026 rebrand announcement; “national register of approved plumbing installers”; WaterSafe Register’s own statement that it is “backed by the drinking water regulators for England, Wales, Scotland and Northern Ireland, and supported by water companies across the UK”). https://www.watersafe.org.uk/news/latest_news/plumber-register-gets-new-name-to-help-householders-hire-safely/

²² Thames Water — Find a plumber (current consumer guidance recommending choice of WaterSafe-approved contractor recognised by water company schemes including WIAPS). https://www.thameswater.co.uk/help/home-improvements/find-a-plumber

Additional water company emergency contacts (referenced in the safety note)

• Affinity Water — emergency line 0345 357 2407 (24/7); leak reporting freephone 0800 376 5325. Contact us hub: https://www.affinitywater.co.uk/contact (with dedicated emergency-routing pages https://www.affinitywater.co.uk/contact/nowater and https://www.affinitywater.co.uk/contact/reportaleak)
• SES Water — emergency line 01737 772000 (24/7). Emergency contact page: https://www.seswater.co.uk/household/help-support/noticed-a-problem
• Essex & Suffolk Water — heavy leak / burst freephone 0800 526 337 (24/7); no water 0345 782 0999. Emergency helplines page: https://www.eswater.co.uk/emergency/emergencyhelplines/

---

Last reviewed

Last reviewed: April 2026. Emergency numbers verified April 2026. This guide is editorially independent. It includes a disclosed reference to the VerifiedPlumbers London directory in section 11. Reviewed against Thames Water’s published Customer Side Leakage Code of Practice and consumer guidance (including dedicated consumer pages on inside and outside stop valves, and Find a plumber), the Water Industry Act 1991, the Water Supply (Water Fittings) Regulations 1999, the Water Supply (Water Quality) Regulations 2016, Drinking Water Inspectorate guidance, the Landlord and Tenant Act 1985, the Housing Act 2004, the Homes (Fitness for Human Habitation) Act 2018, GOV.UK Housing Health and Safety Rating System guidance, WaterSafe Register scheme guidance, Gas Safe Register guidance, and HSE electrical safety guidance.