Planning your works

Last reviewed:
We’ll share the costs of your work if you’re a ‘qualifying authority’, as defined in the New Roads & Streetworks Act 1991. This means you must be one of the following and be engaged in work directly associated with a highway:

  • A highway authority – for example, Highway England or a local council
  • A bridge authority – for example, Network Rail or a local council
  • A railway infrastructure provider – for example, Network Rail or Transport for London.

The Act defines a number of stages for you to be able to work in the street, and we can’t miss any – so you won’t be able to pass to the next stage of the process if the previous stage is incomplete.

If you’re one of the above organisations, the cost-sharing provisions of the Act apply to you. However, if you’re one of the following, or any of the above bodies involved in developing a site, please refer to the guidelines within our working near our pipes page.

  • A developer carrying out works under Section 106 of the Town & Country Planning Act or Section 278 of the New Roads & Streetworks Act, as a condition of receiving planning permission from a local/regional council
  • A developer constructing/modifying access roadways to a development site, including vehicle crossovers
  • A local/regional council developing or modifying council-owned sites, such as estates, offices, garages, access roadways and vehicle crossovers
  • A railway operating company or infrastructure provider developing or modifying railway premises, such as stations, offices and depots
  • A bridge owner for a structure which crosses or carries a non-adopted highway
  • A utility company laying new assets or modifying existing ones, even if in an adopted highway.     

Any of the above engaged in street excavations, transporting abnormal height loads or engaged in heavy vehicle movements that could affect our plant and apparatus, should also follow the guidelines within our working near our pipes page.

Please also see:

Water main diversions Sewer diversions

Checking the location of water mains and sewers

If you’ve not already done so, your first step – known as C2 under the Act – should be to check whether we have any pipes or other equipment near your planned work.

You can do so via our asset location search service, Thames Water Property Searches. Order online from or call 0845 070 9148 (Monday to Friday, 9am to 5pm).

Request a budget estimate

If you’re not sure whether your planned work might affect our pipes or other equipment, please email our Development Control team, stating the work you’re planning and how close it is to our assets. If it does have an impact, you’ll need to request a budget estimate from us, as set out under section C3 of the Act.

Please make sure you contact us at an early stage and tell us about your full scheme, rather than part of it. You should note that we’ll provide a quote for only one scheme, rather than a range of options. We'll also make a charge if you request a re-estimate of the same scheme at a later date.

Your request needs to be set out in a letter, which you can either email to the above address, including the words ‘Working in the street’ or send to us at:

Thames Water Development Planning
Maple Lodge Sewage Treatment Works
Denham Way

In the email or letter you’ll need to tell us:

  • The client – i.e. the qualifying authority with whom we’ll have a financial relationship
  • The consultant / agent / contractor (as applicable)
  • A brief, general summary of your scheme
  • An indicative programme for your works
  • The source and proportion of funding from highways (or other) budget
  • Drawings in .pdf and CAD formats, which identify the location and layout against an Ordnance Survey background.

In addition, we’ll require a letter of appointment if our financial relationship will be with another organisation, rather than directly with the qualifying authority.

You’ll also need to provide the same information if you’re requesting an estimate under the Transport & Works Act 1992, which covers rail schemes.

What we’ll do

Assuming you’ve provided us with all the information set out above, we’ll carry out a high-level review and produce a budget estimate for you.

Alternatively, if there’s no need to divert our pipes, we’ll provide a protection letter, setting out how to avoid damaging our equipment during your work. We may also direct you to another team or request further details of your scheme.

Under the Act, this initial estimate is free. Within it we’ll tell you the design fee you’ll need to pay if you require a revised estimate – for example, if a delay means you need an update at a later date – or to obtain a C4 detailed estimate.

Our timescales

We’ll acknowledge receipt of requests within seven days.

For single diversions, we’ll provide an estimate within four weeks.

For multiple diversions, we'll give you an anticipated date by which we’ll provide you with our C3 budget estimate. Again, we’ll provide this date within four weeks of your request.

More complex schemes are likely to take longer. We’ll consider the entire project scope and its effect on our water and/or wastewater networks. We’ll provide procurement timescales at this stage for any items that are unusual or difficult to source.