There is no Thames Water badge
The phrase people type is "Thames Water approved contractor". The thing that exists is an approved contractor under the Water Supply (Water Fittings) Regulations 1999, registered through WaterSafe. Thames Water point at that register; they do not run it, and they do not assess anyone themselves.
Their find a plumber page splits the advice in two. For work inside the home they recommend a WaterSafe approved plumber. For the underground pipe supplying your property, up to the internal stop valve, they say you may want specialist groundwork contractors, and recommend a WaterSafe approved contractor, "recognised by water company schemes APLUS, WaterMark and WIAPS to carry out specific types of work".
Note "specific types of work". That qualifier is doing more work than most people reading the page realise, and the rest of this page is about what it means. If you want the shorter version of who owns the register, we have written that up separately as where the Thames Water approved plumber list actually is.
Where the status comes from
Approved contractor is a statutory category, not a trade badge. The Water Fittings Regulations use it, and the Water Industry Act 1991 gives it teeth in one specific place: section 73(1A). If a water fitting installed, altered, repaired or connected on or after 1 July 1999 causes contamination, waste, misuse or undue consumption, it is a defence to prove the works were carried out by or under the direction of an approved contractor and that the contractor certified to the person who commissioned the works that the fitting complied with the regulations.
So the approval buys two things. A narrow exemption from advance notification, covered below, and a certificate that carries a statutory defence if the work is later blamed for a problem. It does not buy a warranty, a Thames Water endorsement, or any assessment of whether the firm can find a leak.
The register itself is made up of four approved contractor schemes: APHC, CIPHE, SNIPEF and WIAPS. In the Thames Water region the one that comes up most is WIAPS, the Water Industry Approved Plumbers' Scheme, managed by Water Regs UK on behalf of most water companies in England and Wales — and it is the scheme Thames Water tell plumbers and groundworkers in their region to join. The detail of what membership requires is on our page on what WaterSafe approval means.
What the exemption actually exempts
Regulation 5 says that anyone proposing to install a water fitting in connection with a listed operation must notify the water undertaker, must not start without consent, and must comply with any conditions. The undertaker has ten working days to withhold consent or attach conditions. Say nothing in that window and consent is deemed granted unconditionally.
The listed operations include erecting a building, extending or altering a water system on premises other than a house, a material change of use, large ponds and pools, and a set of named fittings. Then regulation 5(2) disapplies the whole requirement — but only for an approved contractor, and only for three of those entries.
| Listed work | Notification needed? |
|---|
| Extending or altering a water system on premises other than a house | Not if an approved contractor does it |
| A bidet with an ascending spray or flexible hose | Not if an approved contractor does it |
| A reduced pressure zone valve assembly or similar fluid category 4/5 protection | Not if an approved contractor does it |
| Water system laid outside a building shallower than 750mm or deeper than 1350mm | Yes, approved contractor or not |
| Erecting a building, material change of use, large pond or pool | Yes, approved contractor or not |
That is the entire exemption. Three categories. Two of them are things most houses never have.
The supply pipe case, which is the one people mean
Almost everyone searching this phrase has a supply pipe problem: a Thames Water letter, a wet patch on a driveway, a meter that will not stop turning. So, precisely:
- Repairing a leak on an existing supply pipe is not in the regulation 5 table at all. Nobody has to notify, approved or otherwise. The regulations still govern the work itself — materials, backflow protection, depth — but there is no consent to wait for.
- Laying a new or replacement supply pipe is notifiable if it ends up outside 750mm to 1350mm cover, and regulation 5(2) does not rescue an approved contractor from that one.
- Work in the public highway is outside the approval entirely. Thames Water state that approved companies and persons cannot work in the public highway without consent from the local highway authority. If the connection to the outside stop valve cannot be reached by digging on your side of the boundary, that is a separately quoted Thames Water job on top of whatever your contractor charges.
What approval does change on a supply pipe is a different thing: once Thames Water have confirmed a leak on your side, you have four weeks to fix it, and their leaks page reserves a right — if you did not use a WaterSafe approved plumber, they may come out to check the work and charge you for extra repairs they think are needed. Whose pipe it is in the first place is a separate question, and we cover it in who is responsible for a leak outside the house.
What is required of whoever does the work
This part does not depend on approval at all. The Water Fittings Regulations apply to the installer, approved or not: fittings must comply, workmanship must be adequate, backflow protection must suit the fluid category. Section 73 makes causing contamination or waste an offence regardless of who did it. Approval gives a defence; it does not create the duty, and its absence does not remove it.
Two practical things to ask for, whoever you use. First, a certificate of water regulations compliance after the work — Thames Water ask you to obtain one, and it is the document section 73(1A) turns on. Only an approved contractor can issue that certificate. Second, if the firm is on the register, the name of the approved individual: approval attaches to named persons within a company, and Thames Water advise making sure the work is carried out or witnessed by one of them.
Why your borough does not change the answer
This phrase gets searched borough by borough — Lewisham, Hackney, Newham, Southwark, Ealing, Wandsworth. The answer is identical in all of them. The Water Fittings Regulations are national. The WaterSafe register is national. Thames Water's guidance is region-wide.
One thing is genuinely local, and it is the highway. The local highway authority for most streets in London is the borough council, so if the work crosses the footway or carriageway, the consent comes from your borough and not from Thames Water. That is a permit question, not an approval question, and it is why a driveway repair and a repair that reaches the outside stop valve are different jobs with different paperwork.
How to search the approved contractor list
The list people want is the WaterSafe register. It is free, it is searchable, and it is the same list Thames Water send you to. To use it well:
- Search by your postcode, not your borough or county. The results are firms that cover that postcode, which is more useful than a county name.
- Filter for the type of work. An approved plumber who fits bathrooms is not necessarily set up to excavate a driveway and replace a supply pipe. For the underground pipe, you want a firm that says it does groundwork or external supply pipes.
- Check the named person. Approval attaches to individuals within a firm. Ask which approved person will do or witness the work, and check that name, not only the company.
- Ask for the compliance certificate up front. If the firm will not confirm it can issue one at the end of the job, you have learnt something useful before any digging starts.
If a firm's website says "Thames Water approved" and you cannot find it on the register, treat the claim as marketing.
Outside London: check who supplies your water first
Searches for an approved contractor in Essex, Kent, Hertfordshire, Bedfordshire or Middlesex often start from the wrong company. Thames Water's water supply area does not match the counties around London, and in many of those places a different company supplies the water even where Thames Water deals with the sewerage. Some outer London postcodes are the same.
The name at the top of your water bill is the company whose leak rules, repair deadlines and leak allowance apply to you. The approval question is answered the same way everywhere, because the WaterSafe register is national. The rules on who pays for what are set by your supplier, so read theirs before you act on a Thames Water page, including this one.
If you just need the leak found and fixed
For most people with a letter from Thames Water, the approved contractor question is secondary. The urgent part is the four-week repair window. Start with where the leak is. If it is on your side of the boundary, it is a mains supply pipe repair, and the first step is locating it accurately so that the excavation is one hole rather than a trench. If you are not sure the leak is even outside, a meter test will tell you whether water is still passing with every tap off. When the repair is done, keep the invoice: it is the proof Thames Water ask for if you then claim a leak allowance on the water you lost.
What we are, and what we are not
We are an independent London leak detection and repair business. We are not a WaterSafe approved contractor, and we are not approved, endorsed or appointed by Thames Water. If a page anywhere tells you a firm is Thames Water approved, check the WaterSafe register rather than the website — including ours.
That matters for choosing correctly, and Thames Water's own leaks page is straightforward about there being two routes: arrange the repair through your home insurance if you are covered, and if not, use "an approved plumber or leak detection specialist". Detection is the half we do. We find the leak, prove it, and repair it. If your job needs a compliance certificate or a notifiable installation, use an approved contractor for that part, and we will say so rather than take the work.
Our rate is £150 an hour, agreed before we attend, with no call-out fee. If we do not find the leak you do not pay for the time we spent looking, and a detection visit comes with a written report you can put in front of an insurer for a trace-and-access claim — what the policy then covers is the insurer's decision, not ours. Our pricing is published in full.
