0800 520 0043contact@cascadewaterservices.co.uk

New supply pipe installation across London

Extensions, flat conversions, annexes, basements and new plots. A new private supply needs pipework installed to the water regulations — and, where it means a new connection at the main, an application to the undertaker that is best started before the build is finished.

New supply pipe in London?

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The service

The pipework is quick. The application is not.

London creates new supplies constantly: a house split into flats, a rear extension with its own kitchen, an annexe or garden room, a basement dug out under a terrace, a plot infilled between two others. Each needs a private supply pipe, and some need a new connection at the main.

The pipework itself is a day’s work. What sets the timescale is the connection application to the undertaker — Thames Water across most of the capital, Affinity Water and others in parts of it. That process has its own dates, and it does not accelerate because a kitchen is fitted and the completion date has moved.

So we treat the application as the critical path and the installation as the easy bit. We prepare and manage the application, install to the Water Supply (Water Fittings) Regulations, and pressure test and certify before it is signed off.

What we do

Size it, apply early, install and certify.

Depth measurement taken to confirm correct cover over a newly installed supply pipe
Sized for the finished use
01

Size the supply for what the building will actually be

A conversion into four flats does not draw what one house drew. We size the supply against the intended occupancy and fittings rather than matching whatever is already there, and establish whether the existing connection can carry it or a new one is required.

  • Demand assessed against the finished use, not the current one
  • Existing connection capacity checked before assuming a new one
  • Separate supplies and metering arrangements advised where units are split
  • Route planned around existing services and the building line
Ferrule and new blue MDPE service connected to a water main
Application on the critical path
02

Prepare and manage the connection application

Where a new or altered connection at the main is needed, the application goes to the undertaker and their programme applies. We prepare it, submit it and deal with them through it — started early, it runs alongside the build; started late, it becomes the reason the building cannot be occupied.

  • New connection applications prepared and submitted
  • Liaison with Thames Water, Affinity Water or the relevant undertaker
  • Highway permits arranged where the connection crosses the footway
  • Realistic dates given, based on their process rather than optimism
Several new service connections taken from a water main on a London site
Tested and certified
03

Install, test and certify

Blue MDPE laid at the correct depth, ducted or sleeved where it passes through the structure, connected to a new internal stopcock, then pressure tested and flushed. On a new supply the certification matters — it is what a building control inspector, a surveyor or a buyer will ask for later.

  • Installed to the Water Supply (Water Fittings) Regulations
  • Sleeved through the wall or slab so it can be withdrawn later
  • Pressure tested before backfill and on completion
  • Certification issued for the finished installation

Why Cascade

Accredited for the connection, not just the pipe.

  1. 01

    Accredited up to and above 355mm

    Mains and service connections across the full size range, so every London job is within our own accreditation rather than referred on.

  2. 02

    We manage the undertaker

    Applications prepared, submitted and chased. Being an accredited contractor on their network makes that exchange considerably shorter than a homeowner doing it alone.

  3. 03

    LRQA WIRS accredited

    WIRS-accredited to undertake eligible self-lay and contestable works within our accredited scope — plus WaterSafe and WIAPS for work on potable systems.

  4. 04

    Trenchless where the ground allows

    A new run to an annexe or garden room usually crosses finished ground. Moling gets it there without opening the lawn or the paving.

  5. 05

    Certification you can hand on

    Test records and certification for the installation, which is what gets asked for at sale, survey or building control sign-off.

Independently assessed

Full accreditation detail on the about page.

Technical detail

What a new supply has to satisfy.

Material
Blue MDPE
Polyethylene to BS EN 12201, blue for below-ground potable water, jointed without solvent and tolerant of ground movement.
Typical size
25mm
Standard for a single dwelling. Conversions into multiple units, or properties with high simultaneous demand, are sized up accordingly rather than by default.
Accredited mains & services
355mm and above
Cascade is accredited for mains and service connections up to and above 355mm, covering domestic through to large commercial and development demand.
Depth of cover
750–1350mm
No less than 750mm and no more than 1350mm below ground outside a building — deep enough to be frost-free, shallow enough to be reachable.
Entry into the building
Ducted or sleeved
Where the pipe passes through a wall or slab it is sleeved, so it can be withdrawn and replaced later without breaking out structure and so building movement is not transferred to the pipe.
Statutory basis
s.45 WIA 1991
Section 45 of the Water Industry Act 1991 sets out the undertaker’s duty to connect premises for domestic purposes — the statutory footing for a new service connection.

  • Start the application before you need the water

    The undertaker’s timescale is theirs. Applications submitted early run in parallel with the build; submitted late, they become the single reason a finished building cannot be occupied.

  • Splitting a house means deciding on metering early

    Whether converted units take separate supplies and separate meters, or a shared supply with sub-metering, affects both the connection application and the pipework layout. It is cheaper to decide before the walls go up.

  • Basements change the route, not just the level

    A basement conversion often moves the point of entry and can put the incoming supply below the water table. Both are design questions, settled at survey rather than on site.

Common questions

Before you enquire.

The questions we are asked most often about this service, answered without the sales gloss.

See all FAQs
Do I need a new supply pipe for an extension or annexe?

It depends on whether the existing supply can carry the added demand and whether the new space is a separate dwelling. An extension sharing the existing plumbing often does not need a new supply; an annexe, a garden room with its own facilities, or a unit being let separately usually does. We assess the existing connection before assuming a new one is needed.

How long does a new water connection take in London?

The pipework is typically a day. The connection application to the undertaker is what sets the overall timescale, and that is their process rather than ours — Thames Water across most of the capital, Affinity Water and others in parts of it. Started early it runs alongside the build; started late it holds up occupation. We will give you realistic dates rather than optimistic ones.

Can you handle the application as well as the installation?

Yes, and it is usually the more valuable half. We prepare and submit the connection application, deal with the undertaker through it, and arrange any highway permits needed where the connection crosses the footway.

What size supply pipe do I need?

For a single dwelling, 25mm is standard. A conversion into flats, a property with several bathrooms drawing simultaneously, or a small commercial unit will need sizing against actual demand rather than defaulting. We are accredited for mains and service connections up to and above 355mm, so whatever the demand, the connection is within our own accreditation.

Will the new pipe be certified?

Yes. It is pressure tested before backfill and again on completion, flushed through, and certification is issued for the installation. That paperwork is what gets asked for at building control sign-off, at survey, or when the property is next sold.

Can you install without digging up the garden?

Usually. Trenchless moling runs the new pipe underground between two small pits, so lawns, paving and planting between them are untouched. Where the ground will not take a mole — made ground with rubble is common in inner London — we will tell you before starting and reinstate any excavation properly.

London installation enquiry

Tell us what is being built, and when it completes.

The nature of the work, the postcode and your target completion date are enough for us to say whether a new connection is needed and whether the undertaker’s timescale fits your programme.

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What a new supply usually connects to.