Thames Water Approved Plumber: What WaterSafe Approval Really Means
Thames Water does not send its own plumber to fix the pipe on your side of the boundary. It recommends WaterSafe approved contractors. Here is what that approval covers, how to check it, whose pipe is whose, and how to brief a contractor after a leak notice.
There is no separate list of "Thames Water approved plumbers" that Thames Water sends out to homes. What Thames Water does is recommend a WaterSafe approved plumber. WaterSafe is the national register of plumbers who belong to an approved contractor scheme under the Water Supply (Water Fittings) Regulations 1999, and you can check any plumber on watersafe.org.uk by postcode. An approved contractor must give you a signed certificate saying whether the work complies with the Regulations, which is the paperwork Thames Water asks you to get. Approval does not make the plumber a Thames Water contractor: your contract is with the plumber, and Thames Water does not guarantee their work. The pipe from the outside stop valve at your boundary into your home is yours, and if it leaks you must arrange the repair within four weeks. Keep the plumber's details and invoice, because the leak allowance claim needs them. For a supply pipe leak trace and repair, call Emergency Repairs London on 0207 046 1363.
"Is your plumber Thames Water approved?" is one of the first questions homeowners ask us after a leak letter lands on the doormat. It is a sensible question, but it rests on an assumption that is usually wrong: that Thames Water keeps its own panel of plumbers and will send one round to fix the pipe under your front garden. It does not. What Thames Water actually does is point you to the WaterSafe register and leave the choice, the contract and the bill with you.
This guide covers what "approved" means under the water regulations, how to check a plumber, which pipe is yours, and what evidence to keep for a leak allowance claim. If you already have a leak notice and want the pipe traced and repaired, call Emergency Repairs London on 0207 046 1363.
What "Thames Water Approved" Actually Means
The legal basis is the Water Supply (Water Fittings) Regulations 1999, which exist to stop the public supply being contaminated or wasted. The Regulations define an approved contractor as someone approved by the water company for the area, or certified as an approved contractor by an organisation the regulator has specified in writing. In practice, for most plumbers that means membership of an approved contractor scheme.
WaterSafe brings those schemes together in one place. It describes itself as a free online directory and national accreditation body for competent, qualified plumbers, water supply pipe installers and other water specialists across England, Scotland, Wales and Northern Ireland.
Thames Water's own advice is short and clear. For plumbing inside your home, it recommends choosing a WaterSafe approved plumber, and it notes that these plumbers are recognised by the water company schemes APLUS, WaterMark and WIAPS. For the underground pipe that feeds your property, up to the internal stop valve, it says you may want to use a specialist groundwork contractor. It also states plainly that your contract is with the plumber or groundworker, not with Thames Water, and that it cannot vouch for their availability or guarantee their work.
So when a firm calls itself "Thames Water approved", ask whether it is on the WaterSafe register, and under which name.
How to Check a Plumber on the WaterSafe Register
Checking takes a couple of minutes and costs nothing:
- Go to watersafe.org.uk and pick the type of work you need.
- Enter your postcode. If you are not sure of it, the first half works (for example "E15" or "UB8").
- Browse the approved plumbers and contractors listed near you.
- If a plumber has told you they are approved, ask for the exact business name they are registered under and search for it. Trading names and registered names are often different.
- Do the check before any work starts, not when the invoice arrives.
What an Approved Contractor Can and Cannot Sign Off
Approval matters for two practical reasons: paperwork and notification.
The certificate. Regulation 6 says that when an approved contractor installs, alters, connects or disconnects a water fitting, they must give the person who commissioned the work a signed certificate stating whether it complies with the Regulations. Thames Water asks customers to make sure they receive a certificate of water regulations compliance from the plumber or groundwork contractor once the job is finished. On a lead pipe replacement, Thames Water says an approved plumber's certificate means no open trench inspection is needed.
Notification. Regulation 5 lists work that must be notified to the water company before it starts, with the company's consent. If the company does not respond within ten working days, consent is treated as given. The list includes any water system laid outside a building less than 750mm or more than 1350mm below ground, which matters for supply pipes. WaterSafe says its approved contractors can carry out certain work without telling the water company first. Under the Regulations that exemption is narrow. It covers only three items: extending or altering a water system in premises other than a house, bidets with an ascending spray or flexible hose, and certain backflow protection valves.
What approval does not mean: it does not make the plumber a Thames Water contractor, it does not mean Thames Water has inspected your job, and it does not move responsibility for your pipe to anyone else. It tells you the plumber belongs to a recognised scheme and will certify the work.
Whose Pipe Is It? Supply Pipe vs Communication Pipe
Before you appoint anyone, be sure the leak is actually yours. Thames Water is responsible for the water mains and for the communication pipe that links your supply pipe to the main. You own the supply pipe, which Thames Water describes as starting at your outside stop valve and ending at your inside stop valve. The outside stop valve usually sits at your property boundary.
| Section | Where it runs | Who arranges the repair |
|---|---|---|
| Water main | Under the road or pavement | Thames Water |
| Communication pipe | From the main, usually to the outside stop valve at your boundary | Thames Water |
| Supply pipe | From the outside stop valve, under your garden or driveway, to your inside stop valve | You (your landlord if you rent) |
| Internal plumbing | Everything after the inside stop valve | You (your landlord if you rent) |
| Shared supply pipe | One pipe serving more than one property | You and your neighbours jointly |
If the leak is on the main or the communication pipe, report it to Thames Water on 0800 316 9800, which is open 24 hours a day. Fixing its own pipes is Thames Water's job. For the step-by-step test that shows which side of the boundary a leak is on, see our guide to Thames Water leak responsibility in London. If the pipe is lead, Thames Water says it can also replace any lead pipework that belongs to it when you replace yours. You need to apply and be planning your own replacement within three months. Our lead supply pipe replacement guide covers that route.
After a Leak Notice: Repair, Evidence and the Allowance
Thames Water is clear that whether you find a leak yourself or it confirms one at your property, you must fix it within four weeks. If you do not arrange the repair in that time, it may serve a legal notice under Section 75 of the Water Industry Act 1991. On a meter, it also says it will no longer be able to cover all the costs of the leak on your bill.
Thames Water says it may be able to help with a repair if you are registered for one of its financial support schemes or its priority services register, so check that before you assume the whole cost falls on you.
For the leak allowance, Thames Water lists four conditions:
- the leak is repaired within four weeks of Thames Water first notifying you, or of the leak being identified;
- Thames Water can confirm the repair from a plumber's details and invoice, or its own job number if it did the work;
- the leak was not fixed under Section 75; and
- the allowance is claimed within three months of the repair date, even if no bill has arrived yet.
The process uses two forms: a leak fixed form, then the leak allowance form. Thames Water works out the allowance by comparing the water you used in a similar past period with what your meter recorded during the leak.
Keep this file from day one: the leak notice and its date, the contractor's name and WaterSafe listing, the compliance certificate, a dated invoice that names the address and describes the supply pipe repair, photos of the exposed pipe and the finished repair, and meter readings taken before and after. The full claim walkthrough is in our guide on how to claim the Thames Water leak allowance.
Got a Leak Notice and a Four-Week Clock?
We trace and repair supply pipe leaks across London and give you a dated invoice describing the repair for your leak allowance claim. Our call-out fee is £60.
Call 0207 046 1363How to Choose and Brief a Supply Pipe Contractor
On an underground leak, most of the cost is finding it and getting to it, so method matters as much as price. Ask before you book:
- Are you on the WaterSafe register, and under what name? Then check it yourself.
- How will you find the leak? A contractor who plans to dig along the whole run before testing anything will cost you more in reinstatement.
- Will you confirm the leak is on my side before you dig? If it turns out to be on the communication pipe, it is Thames Water's to fix.
- Will you notify Thames Water if the work needs it? A new or rerouted pipe laid outside the 750mm to 1350mm depth range is notifiable.
- What will the invoice say? It should give the address, the date, where the leak was, what was repaired and the contractor's details.
- Will I get a compliance certificate? An approved contractor must provide one.
- What does reinstatement include? Get it in writing: backfill, paving, tarmac or turf.
- How are you charging? Ask for the call-out, labour rate and any fixed quote in writing before chargeable work starts.
Brief them well. Send a photo of the leak notice, your meter readings, where your stop valves are, any damp or soft ground, and whether the supply is shared with a neighbour. If it is shared, read our guide to shared supply pipe leaks and neighbour responsibility before work starts.
A fair process looks like this: diagnosis first, a written price before any chargeable work, digging only where the leak has been found, a pressure-tested repair, reinstatement as agreed, and paperwork on the day. Our own published rates are a £60 call-out, then labour from £110 an hour on weekdays or £140 an hour out of hours.
Does It Matter Which London Borough You Are In?
The pipe rules do not change at a borough boundary. Whether you are in Newham, Waltham Forest, Ealing or Merton, the same Regulations apply, the supply pipe is still yours, and the WaterSafe postcode search works anywhere.
What can change is your water company. Most of London is supplied by Thames Water, but not all of it. Essex and Suffolk Water supplies Barking and Dagenham, Havering and Redbridge. Affinity Water supplies Harrow and Hillingdon and parts of Barnet, Brent, Ealing and Enfield. SES Water supplies parts of south London, including Sutton, Merton and Croydon. If you live in one of those areas, the leak notice, repair deadline and allowance process are your supplier's, not Thames Water's. Check the company name on your water bill before you follow any guidance, including ours.
If you are unsure whether a leak is on your pipe, or you need it traced and repaired within the four weeks, call Emergency Repairs London on 0207 046 1363. We cover every London borough.
FAQs
Does Thames Water have its own approved plumbers?
How do I check if a plumber is WaterSafe approved?
Do I have to use a WaterSafe plumber to fix a leak on my supply pipe?
Will Thames Water fix a leak on my side of the boundary?
What paperwork do I need after a supply pipe repair?
I live in Havering, Hillingdon or Sutton. Is Thames Water my water company?
Save the number: 0207 046 1363. Supply pipe leak tracing and repair across London.
Valentin N., Operations Director, Emergency Repairs London
Key Takeaways
- Thames Water recommends a WaterSafe approved plumber for work on your plumbing. It does not run its own list of plumbers who come out to fix customer pipes.
- WaterSafe is a free national register of plumbers who belong to an approved contractor scheme. You can search it by postcode at watersafe.org.uk.
- Under the Water Supply (Water Fittings) Regulations 1999, an approved contractor must give you a signed certificate stating whether the work complies. Ask for it on every job.
- Approval does not make a plumber a Thames Water contractor. Your contract is with the plumber, and Thames Water says it cannot guarantee their work.
- Thames Water owns the main and the communication pipe. You own the supply pipe from the boundary, where the outside stop valve usually sits, up to your inside stop valve.
- Once you find a leak on your side, or Thames Water tells you about one, you have four weeks to fix it. After that Thames Water may serve a Section 75 notice.
- The leak allowance needs the plumber's details and invoice, a repair within four weeks, and a claim within three months of the repair date.
- Parts of outer London get their water from Affinity Water, Essex and Suffolk Water or SES Water. Check the company name on your bill before following any supplier's process.
