Build over sewer self certification

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.

We do not normally allow structures to be built over or near water mains.  If you find one, it's important to contact us to discuss next steps on 0800 9172652.

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.

There are two types of application:

  • Self-Certification - A shorter process where you can 'self certify' as long as you meet certain criteria
  • Full legal application - A more detailed process, usually needed for more  complicated or higher risk work, that involves our legal team

How do you establish which application type you need?

The starting point is to complete our self-certification triage.  If you meet the self certify criteria, you can complete an application form and we will send you an email confirming whether your form has been approved.

If you don't meet the self certify criteria, you'll be asked to complete a full application.

Our detailed guidance notes are a good start and include more detail on the two types of consent that we offer.

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.