Self lay

If you're building multiple properties on a site that will have a new road, then you'll probably need a new water main.

Most new development sites which have a new road need a new water main, which we'll then connect to our existing network. The new main will serve the site and each property will then be connected to the new main via their own individual service pipe.

There are two ways you can apply for a new water main:

  • Self lay, where an accredited self-lay contractor will build the water main for you rather than us
  • Water main requisitioning, where we will build the water main for you

This page details the self lay option. Please click here for the water main requisition option.

What will the service provide

A self-lay water main is where you choose to have your new water main laid (and sometimes designed) by an accredited self-lay contractor instead of us. Once your self-lay contractor has laid the pipes, we’ll check that they meet our terms and will adopt them into our network.

If you choose a self-lay contractor:
  • Before any work starts, you’ll need to enter into a legal agreement with us, the landowner and the self-lay provider (SLP)
  • The SLP will also need to be Water Industry Registration Scheme (WIRS) accredited. More information on WIRS can be found here. Occasionally, we may accept companies that are not fully accredited, but we reserve the right to assess an SLP’s competency if it isn’t WIRS accredited
  • You need to keep us updated on the progress of the work

How much will it cost?

There are a few charges related to this service:

  • An initial application fee
    • This is an upfront non-refundable fee of £2,500+VAT, to be paid on application, using a valid credit or debit card. Once the works have been completed, we’ll then deduct the application fee from your pre-development payment, so you’ll just have to pay the difference.

For self-lay work, we will pay you for doing the work to reflect the future income we are going to receive from the scheme. We do this via a system of two payments:

  • Pre-development payment
    • This a payment you will make to us before starting the work.
    • It’s either the cost of delivering the non-contestable works or the estimated commuted sum for delivering the scheme, whichever is least.
    • It’s a variable charge, dependent on the specifics of each scheme.
    • In most circumstances, this is refunded on completion of the scheme by an accredited self-lay provider (SLP).
  • Asset payment
    • This is a payment we make to you or the SLP, which reflects the cost we’d have to pay our contractor for doing the work (the contestable works), minus the commuted sum. The commuted sum is the difference between the scheme’s projected income versus the costs of delivering that scheme.
    • It is paid to you after we’ve adopted the water main and have undertaken a final account to calculate the final asset payment. We also make interim asset payments where the scheme is vested in multiple phases.
    • For example, if the scheme would normally cost Welsh Water £10,000 to do the work ourselves or via our contractor, and guarantees us a future revenue of £9,000, then the asset payment would be worked out by £10,000 minus the £1,000 difference, meaning the final asset payment would be £9,000+VAT.

For information on our charges, visit our schedule of charges here.

How can I apply?

If you would like us to do your design for you, then head straight to our self-lay application form. If you are doing your own design, then you’ll need to submit our point of connection form before the self-lay application to

To avoid any delays, once your self-lay scheme has moved into construction, please keep us up to date with your programme. The forms at the very bottom of this page need to be submitted at various stages of construction to

Where can I find more information?

  • Our guidance notes and design guide below are a good start.
  • Water UK has a helpful code of practice which you can download here.
  • Lloyds Register has a useful search tool for Water Industry Registration Scheme (WIRS) accredited self-lay contractors.
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Self-lay guidance notes

PDF, 163.1kB

We’d advise everyone to take a read of our detailed guidance notes here before making an application.
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Self-lay design guide

PDF, 5.7MB

This document details the specifications of our network.

Self-lay forms

Self lay point of connection application form

64.1kB, PDF

SLN1Commencement of mainlaying 190719

85kB, DOCX

SLN2Annex1Sampling Request 190719

94.9kB, DOCX

SLN2Provision of supply for pressure and bacteriological testing 190719

107.3kB, DOCX

SLN3Request for a permanent supply of water 190719

69.6kB, DOCX

SLN4aRequest for DCWW to operate a valve for B2B connection 190719

84.7kB, DOCX

SLN4bNotification of proposed routine contestable mains connection 190719

68.1kB, DOCX

SLN5aNotification of completed routine mains connection 190719

72.8kB, DOCX

SLN5bNotification of aborted routine mains connection 190719

72.2kB, DOCX

SLN6Notification of commencement of water service connection 190719

66kB, DOCX

SLN7Notification of completed water service connection 190719

56.2kB, DOCX

SLN8Request to meter installation on water selflay scheme 190719

63kB, DOCX

Vesting Certificate 190719

43.8kB, DOCX