Finding out if a sewer is mapped

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If you’re planning building work, it’s important that you find out how close you might be to any public sewers. ‘Mapped’ public sewers are those that appear in the map of public sewers that are maintained by your local water and sewerage company – but a high proportion are unmapped.

A change in legislation meant that in October 2011 we became responsible for an additional 40,000 kilometres of sewers, which if laid end to end would be enough to circle the world. All of these sewers were previously privately owned, and in many cases don’t appear on our records.

This means that when customers apply to build over or near a sewer, we often need to ask them to provide details of nearby sewers and manholes.

How do I know whether there's a mapped public sewer near my property?

You may be able to check its location by visiting your local authority offices to inspect their sewer maps.

Alternatively, you can contact our Property Searches team via thameswater-propertysearches.co.uk or by calling 0845 070 9148 (weekdays, 9am to 5pm), to order an ‘asset location search’ for your property. Please note, there is a charge for providing this.

The search provides information on the location of known water and/or sewage pipes, including details of pipe sizes and direction of flow. We’ll only be able to provide details of pipe depths and cover levels where the data is available.

If the public sewers near my property aren't mapped, how can I apply?

If this is the case, don’t worry. Complete as much of the application as you can, and include as many details as possible in your proposals, even if they’re very basic. Your builder or architect should be able to help you with this.

We’ll also need to know the year in which your property was built, as this will help determine whether a sewer is our responsibility. If it was built in 2011, we’ll require the month.

If your sewers aren’t mapped, please don’t make a payment at this stage. This is because any nearby sewer might be privately owned, and we’d therefore need to refund your payment, which could hold up your work.

If you’ve applied for a full build over agreement, we’ll contact you within 21 days of your application. We’ll discuss your proposal with you, including any details that might need amending.