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Sewer diversion

If one of our sewers runs near your planned works, you may need to divert or change it. Here we’ll take you through the process of applying for a sewer diversion (Section S185 or D185) .

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Types of sewer diversion

Depending on the type of sewer and your works, you may be able to carry out the diversion (Developer-led diversion D185), or we may have to do it (Southern Water-led diversion S185). The legal and financial details will be vary depending upon who is carrying out the work.  

Once we receive your application, we’ll review your proposal and let you know the best design options for the sewer diversion. 

GetConnected portal

Our GetConnected portal lets you submit applications, track their progress, make payments, and manage your projects all in one place.

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You can carry out the diversion if:

  • Your project involves a non-critical sewer

    A sewer is classed as non-critical if it is less than 225m in diameter or less than 3 meters deep

  • It's within your boundary

    The route of the sewer diversion remains entirely within the boundary of your land

We'll need to do the diversion if:

  • It passes through someone else's land

    The route of the diverted sewer passes through third-party land

  • Your project involves a critical sewer

    A sewer is classed as a critical if it’s more than 255mm in diameter and more than 3 meters deep. This includes all rising mains and sewers that have specific operational requirements

  • The sewer to be diverted is a bonded asbestos cement pipe

    This includes pipes described as asbestos cement (AC) and fibre-reinforced cement (FRC) 

Developer-led diversion Southern Water-led diversion
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Developer-led diversion

Below you can find a useful guide — please read it before you get started. We'll be in touch every step of the way to make sure everything runs smoothly. As part of your developer-led application, you will need: 

  • A site plan (.pdf) at 1:2500: development site edged in green and clearly detailing any roads, adjacent buildings and the private pipe run to our network.
  • A site location plan (.pdf) at 1:1250 (or larger).
  •  A drainage layout plan (.pdf) at 1:100 (or larger), showing the location of sewers and manholes on site and up to the connection point.
  • Manhole construction and longitudinal section details (.pdf).
  • Third-party landowner information (if applicable).
  • A copy of your planning consent.
  • A CCTV survey is required if any laterals or drains are connected to an abandoned or diverted sewer. This requirement is subject to technical review as part of the application process.
1

Apply online

Within our GetConnected portal, fill in the online form and pay your application fee. We’ll review your application within five days and confirm if we need more information.

Apply now
2

Application approval

We’ll review your proposal and get back to you within 28 days. If it meets our standards, we will provide you with a compliance letter. This will include the estimate of the cost of adoption and any required fees. 

3

Accept and pay

Once you’re ready to accept, you should make payment for the fees set out in your compliance letter. 

4

Section 185 agreement

We’ll arrange for a legal agreement to be created and signed before the work begins. Our team will also find a suitable time to carry out a commissioning inspection.

5

Request inspections

When you’ve completed the works, you’ll also need to request a sewer maintenance inspection. This inspection will confirm that the works are suitable to be placed on ‘12 months maintenance’ and we’ll give you a provisional certificate. 

6

Final inspection and completion certificate

About three months before your maintenance period ends, you can ask us for a final inspection. Once we’ve checked everything and any remedial work is complete, we’ll send you the final certificate. After that, the sewers will legally transfer to us. 

Southern Water-led diversion

Below you can find a useful guide — please read it before you get started. We'll be in touch every step of the way to make sure everything runs smoothly. As part of your developer-led application, you will need: 

  • A site plan (.pdf) at 1:2500: development site edged in green and clearly detailing any roads, adjacent buildings and the private pipe run to our network
  • A plan (.pdf) highlighting the length of the sewer you would like to divert and the location you would like it moved to if you have a preference
  • Your proposed drawing in a .dwg format. This will need to be compatible with AutoCAD
  • A soil analysis report
  • A copy of the existing wayleave/easement agreement (if available)
  • An application fee will be required. This can be found in our charging arrangement document.  
1

Apply online

Fill in our online form and pay your application and design fees. We’ll review your application within five days and confirm that we have everything we need to move forward.  We may ask for more information. 

Apply now
2

We'll send an initial estimate

Within 12 weeks, we'll check if the diversion is possible, create an outline design and send you a preliminary estimate for the work. If the design is simple, you may not need this, and we’ll provide a detailed design offer straight away.  

3

Accept the offer and pay

 Once you are ready to accept the estimate, we can move on to the detailed design stage. We’ll send you a remittance form which you’ll need to complete and return to us. You’ll also need to pay the detailed design fee.  

4

We'll complete your design

We’ll provide a detailed design. Once we've agreed on this, we'll pass you onto our Project Delivery team. Your assigned Project Manager will be your point of contact and guide you through the next steps. 

5

We'll complete the work

Our Project Delivery team will confirm a start date, schedule and completion date for the onsite work with you. After construction is complete, we'll update our sewer maps with the diverted route. 

Useful guides and documents

Developer Diversion of Sewer Guidance Notes

Download

Developer Diversion of Sewer Guidance Notes

Download

Developer Diversion Example Drawing

Download

New Appointments & Variation

NAV Charging Arrangements 2025-26

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New Connection Charging Arrangements 2025-26

Download

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Get in touch

If you need help choosing which application to make, filling it out, or have any other questions, our team are happy to help.

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Request a call back

If you need help deciding which application to make or how to fill it out, or if you have any other questions, you can ask our team to call you back.

Request a call back
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Submit a query

We’re here to help if you need us. Please fill in the form with as much information as possible to assist us with your enquiry.

Submit a query
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Contact the Developer Services team

If you need help deciding which application to make or how to fill it out, or if you have any other questions, call us Monday-Thursday 9am-5pm, Friday 9am-4pm.

Call: 0330 303 0119

Helpful links

Sewer connection

If you're building a house extension, a new home or a commercial building, or simply making changes to your existing drainage, you may need a new wastewater connection to our sewer network.

Find out how to apply

Building over a sewer

Learn more about why you should consider any nearby sewers while you're planning your project, and how to submit a build over application.

Submit your application

Water Main Diversion

If you need to request a change, diversion, or removal of one of our water mains you will need to apply for a water main diversion.

Water Main Diversion