Building over or near to sewers


It’s our job to collect surface water and wastewater from homes and businesses across Wales and parts of England. And to do this we use our vast network of sewer pipes, over 30,000 km of them in total - that’s enough to stretch to Australia and back! 

Our sewers run under the ground all over our operating area, in streets and gardens, fields and land. So, if you’re extending your property, whether you’re building an extension or a conservatory, the chances are there’ll be a sewer pipe nearby.

That’s why you’ll need to let us know if you’re planning to extend your home, so that we can make sure your home, and our pipes, are protected during and after the build.

If you’re extending your property, you’ll need to make sure you know if there are any water mains, public sewers or drains on your land. It’s a good idea to find out before you begin, so the work goes as smoothly as possible.

If you plan to build over, or within three metres of one of our sewer pipes or lateral drains, you’ll need to let us know – so that we can consider your proposal.

If you are interested in finding out more, our detailed guidance notes are a good start. They’ll help you identify if and what type of consent you need. You’ll then either need to submit a declaration of works form or an application for a formal agreement.

How long will it take?

  • Once we’ve received your application, we’ll aim to give our consent within 14 working days.
  • In some cases, we may need further information from you before being able to decide if the project can go ahead, or if it needs to be changed.

How much will it cost?

Our charge covers the cost of:

–––– Administration of your declaration

–––– Site inspection if necessary

–––– Technical support

–––– Liaison with building control or your approved inspector

–––– Issuing your letter of consent or agreement

  • If we consent to your plan by letter, with no alterations needed to our network, it will cost £93
  • If we consent to your plan by letter, following the completion of alterations to our network, it will cost £481
  • If we consent to your plan by legal agreement, it will cost £587

Don’t forget

  • You can’t start work until we’ve consented to your application.