Sewer diversion

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

Where there is a sewer main affecting your planned development, there may be a need to divert the main. We can assess your proposal and comment on the design options through a sewer main diversion.

Below is a guide on what you need to do when making a sewer main diversion application, including links to make an application on our portal. We often refer to a diversion as a ‘Section 185’.

Decide who will carry out the work

A sewer diversion can be carried out by yourself as a Developer or though us, as explained in the below criteria.

As a Developer, you can carry out the works where the following applies:

  • The apparatus to be diverted is categorised as non-critical.
  • The route of the diversion remains entirely within the boundary of your land.


We would design and carry out the works when:

  • The route of the diverted sewer passes through third party land.
  • The sewer to be diverted is a critical sewer (this includes all rising mains) or there are 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).


The legal and financial arrangements will differ depending upon who is carrying out the works.

Developer Led Diversion

The following information is for when you have decided that you as a Developer will carry out the work.

Developer Diversion – Stage 1 – You Make an Application

All Developer led diversions should be made by applying via our GetConnected portal.

Before you apply, please read our Developer Sewer Main Diversion Guidance Notes which will take you through the process and what is required, including:

  • 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 details (.pdf).
  • Longitudinal section details (.pdf).
  • Third party landowner information (if applicable).
  • A copy of your planning consent.

An application fee of £373.00 (incl. 20% VAT) will be required.

Once your application has been made, our team will review the information submitted and we will respond within 5 days to confirm the documentation is complete or ask for more information if required.

Developer Diversion – Stage 2 – Application Approval

Within 28 days we will technically assess the application and send you our decision on your proposal. We may either give our approval (Compliance letter) or ask for an amendment and further technical information to be provided to us (Non-compliance letter).

When the proposal meets our standards, we will provide you with the compliance letter, with our estimate of the cost for adoption and the fees that will be required as per the below:

  • The full estimate for the cost of adoption (refundable).
  • A supervision fee (non-refundable).

The refundable cost of adoption will be issued in two stages. Stage 1 (80% of the cost) is released when:

  • The Legal Agreement and Deed of Grant of Easement (if required) have been signed.
  • A pre maintenance inspection of the works has satisfactorily been completed by our Clerk of Works.

Stage 2 (20% plus accrued interest) is released when:

  • A final inspection has satisfactorily been completed by our Clerk of Works.
  • A Final Certificate has been issued.

Developer Diversion – Stage 3 – Awaiting Acceptance and Construction

Once you are ready to accept, you should make payment for the fees set out in your GetConnected portal dashboard, this will also be detailed in your compliance letter.

Following this we will arrange for a legal agreement to be created and signed by all parties.

Our team will then find a suitable time to carry out a commissioning inspection.

Developer Diversion – Stage 4 – Maintenance Period and Provisional Certificate

Once construction of the sewers has been completed, you’ll need to request a sewer adoption maintenance inspection and provide:

  • The ‘As Built’ drawings (.pdf).
  • The health and safety file.
  • Any other outstanding requirements.

Please send the request with the above information to Developer.Services@southernwater.co.uk including the sewerage reference number for your application and site location in the email subject line.

We’ll arrange a maintenance inspection to confirm the works are suitable to be placed on ‘12 months maintenance’ and we’ll issue a provisional certificate.

Developer Diversion – Stage 5 – Final Inspection and Vesting

Three months before the end of your maintenance period is due, you should check the sewerage system and make sure no maintenance issues are outstanding, then contact your Assistant Adoption Manager. They’ll organise a final inspection of the adoptable system and will advise if any remedial work is required.

Once we’re satisfied all remedial works have been carried out, our engineer will issue the final certificate of completion. The legal vesting of the sewers will happen soon after.

Southern Water Diversion

The following information is for when you have decided that we will carry out the work.

Southern Water Diversion – Stage 1 – You Make an Application

You can apply for us to undertake the diversion via our GetConnected portal.

Before you apply, please read our Southern Water Sewer Main Diversion Guidance Notes which will take you through the process and what is required, including:

  • 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 main 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 of £2220.00 (incl. 20% VAT).

Once your application has been made, our team will review the information submitted and we will respond within 5 days to confirm that the documentation is complete or ask for more information if required.

Southern Water Diversion – Stage 2 – Receive a Budget Estimate Offer

Within 12 weeks we will assess the initial feasibility, create an outline design and then send you a preliminary budget estimate offer for the works to be carried out, this will include:

  • A budget estimate offer letter, detailing the estimated cost of the scheme and the required detailed design fee.
  • Associated design drawings.
  • A report detailing the scope of works.

In some cases, our team may deem the design to be straight forward that a budget estimate is not required. In this scenario we will let you know this is the case and provide you with a detailed design offer in the first instance. Once ready to accept, you would need to make the full design payment before progressing onto Step 6.

Southern Water Diversion – Stage 3 – Accept Budget Estimate and Pay

Once you have received our budget estimate offer and are ready to accept and pay the fee to progress to detailed design, you will need to do the following:

  • Complete and return the remittance form.
  • Make payment for the detailed design fee.

Once you have completed the above and paid, we will pass the site to our Project Delivery engineering team who will assign a Project Manager as a point of contact for the next steps in the process.

Southern Water Diversion – Stage 4 – Detailed Design and Awaiting Construction

Once the budget estimate design has been agreed and the detailed design fee paid, we will pass the site onto our Project Delivery team for the detailed design coordination. Your assigned Project Manager will confirm the final delivery route before any construction works are scheduled.

Southern Water Diversion – Stage 6 – Work Scheduled and Onsite Dates Confirmed

Our Project Delivery team will confirm a start date, schedule and completion date for the works on site and communicate this to you.

Southern Water Diversion – Stage 7 – Work Complete

After the connection has been made and the inspection of completed onsite work carried out, the diversion will be complete and our maps will be updated of the diverted route. Care must be taken if carrying out any further works on site to protect the asset.

Water Main Diversion

You may also want to find out more about a water main diversion.

 
 
 
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