Where the scheme starts and stops
The confusion in every search for this is the boundary, so start there. Thames Water say they own the communication pipe, which "starts at our water main and usually runs to the outside stop valve at your property boundary", and that they are responsible for fixing or replacing it. You own the internal pipework and the supply pipe, which "starts at your outside stop valve and ends at your inside stop valve".
The lead pipe replacement scheme sits exactly on that line. In Thames Water's words: "If you're replacing lead pipework, we can also replace any lead pipework that belongs to us. This is provided you qualify and are responsible for the pipework." So the order of events is yours first, theirs second. You replace the lead supply pipe running under your garden, path or front steps, they inspect or accept a certificate, and then they replace their lead communication pipe out in the road.
They will not do your side. Nothing on the scheme page offers money towards it either.
Search this subject and you will find a specific supply pipe subsidy quoted as a Thames Water contribution, usually two amounts, one for the pipe and one for something smaller. We have read Thames Water's lead pipe replacement page and its leakage code of practice and neither contains any payment towards a customer's own supply pipe replacement. We are not going to repeat a number we cannot find at source, because you would budget around it.
What Thames Water do say about help with cost is narrower and sits in their leakage code of practice: they will assist with a supply pipe leak at their discretion for customers in their Priority Services Register categories or on their WaterHelp or WaterSure schemes, and they will step in "if there's a risk to life or to our supply network". That is leak repair assistance, not a lead replacement grant, and it is discretionary.
Whether you qualify
Thames Water list the criteria. You can apply if you:
- have a property built before 1970;
- suspect you have lead supply pipework;
- are not aware of Thames Water having already replaced the communication pipe;
- will bring the new pipe to the current outside stop valve or property boundary, in line with the existing valve;
- have located your outside stop valve and confirmed whether your supply is separate or shared;
- plan to replace the lead supply pipe within the next three months — after that, Thames Water say you need a fresh application;
- have decided whether to use an approved or an independent plumber.
Two of those quietly do most of the filtering. "Not aware of Thames Water replacing comms pipe" rules out a lot of London streets where the main was renewed at some point in the last thirty years and the lead left behind is all on private land. And confirming the supply arrangement matters because a great many Victorian terraces are on a shared supply pipe, which the scheme does not separate. Thames Water are explicit: they do not offer services to separate supplies under this scheme.
How to tell whether the pipe is actually lead
Thames Water give four tests, and they work. Unpainted lead is a dull grey. Joints in lead pipe are rounded and swollen where two lengths meet, rather than the sharp collar of a compression fitting. Scratch it gently and lead shows shiny silver underneath. Tap it and lead gives a dull thud, where copper or iron rings.
The place to look is where the pipe rises out of the floor at your internal stop valve, usually under the kitchen sink. If the first 300mm of pipe there is grey, soft and swollen at the joints, the run under your garden is very likely the same. Also worth knowing: lead can be present as solder on copper joints in older internal plumbing, and Thames Water say removing internal lead pipework or solder is yours to arrange with an approved plumber. It is not part of the scheme.
The earthing check nobody mentions until it is too late
In older houses the electrical installation may be earthed to the incoming metal water pipe. Replace that pipe with plastic and the earth path disappears. Thames Water tell you to check your earthing if you have a lead supply pipe, if the supply is single or shared with a neighbour, if you know where your outside stop valve is, or if the house was built before 1966, and to speak to your electricity supplier or a qualified electrician if you are unsure.
Do that before the trench is dug, not after. It is an electrician's job and it is not ours.
Approved plumber or independent plumber
This choice changes the process, not the price of the pipe. Thames Water put it plainly: an approved plumber "will issue a certificate about the work they carried out. No open trench inspection is required", though you still have to send them the certificate. If you use an independent plumber, "the pipe laid within the open trench must be inspected by Thames Water. This must be done before burying."
In practice that means an independent plumber has to leave the trench open and wait for an appointment. On a London front garden, with a party wall on one side and a parked car on the other, an open trench is not a small inconvenience. What "approved" actually means is worth understanding before you choose.
What the new pipe has to be
The replacement is like for like in size and location, with one upgrade: Thames Water say existing smaller pipes of 12–15mm will be replaced with the industry standard 25mm, and anything already larger than 25mm will be matched. To pass their reconnection survey they list what must be done:
| Requirement | Thames Water's specification |
|---|
| Pipe size | 25mm, or like-for-like where the existing is larger |
| Trench depth | Minimum 750mm, maximum 1350mm |
| Internal stop valve | An approved valve fitted |
| Point of entry | Pipe insulated and ducted, laid at minimum 750mm |
| Drain valve | An approved drain valve upstream from inside the stop valve |
| Bedding | Pipe ducted or laid in soft material |
| Alignment | Laid in line with the outside stop valve, with enough excess to reach it |
| Walls | Tunnelled underneath the brick wall or fence, not over or through it |
Where the pipe runs in via a basement or vault, Thames Water say wall breakthroughs are the customer's responsibility. That is the line where a pipe job turns into a building job, and it is the part of this work London flats and converted terraces run into most often. It is also the part we do ourselves rather than hand back to you: see reinstatement.
Timescales
Thames Water aim to complete their side within three months of you qualifying, with reinstatement of the road usually within two working days of the replacement. Before that they have to trace their communication pipe, mark the road and pavement, and get permits and traffic management approved. None of that is fast, and none of it is under your control.
Afterwards they tell you to flush the cold kitchen tap for about two minutes before use until the work is complete, and on the first day after completion to run every tap used for drinking or cooking for ten minutes.
When not to call us
If your only objective is replacing a lead pipe, this is groundwork, not leak detection, and plenty of firms do it. Call us when the lead pipe is also leaking and nobody can say where, when the run disappears under a solid floor or a vault and the trench cannot simply follow it, or when the excavation is going to take out a tiled path, a bay window step or a block-paved drive that somebody then has to put back. That last part is the half most firms leave you with.
Our work is charged at £150 per hour, agreed before we attend, and if we cannot find the leak you do not pay for the time we spent looking. How we price explains it.
