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Existing connections

Once you are connected to the National Transmission System (NTS) you may need to make alterations to your existing connection or disconnect from the NTS. This page provides the information you will need to modify your connection or disconnect.

Modifying an existing connection point

When a customer wishes to modify an existing NTS connection, they need to complete the A2O process by submitting the NTS Connection Application form. The application guide explains how to request an offer for a modification to an existing connection.

Download the application document

Download the application guide



Disconnecting from the NTS is broken down into two category types, which are set out below:


Disconnection (physical)


Decommissioning (complete removal)

Positive isolation from the NTS and the customer’s facilities.

  • Physical air-gap between the two assets

  • Gas is unable to flow

  • National Grid maintains site

Assets on site move into a mothballing preservation state.

Site returned to original state

  • All assets disconnected and removed including the removal of pipeline.

Asset preservation (mothballing)

  • Following disconnection of the assets, we will conduct ongoing site maintenance to make sure the site is safe and preserved if in the event the customer wishes to bring the site back ‘on stream’.

  • As this is a request from the customer, costs for maintenance are payable by the customer.

Asset preservation (mothballing)

  • May be required if the assets are disconnected and the customer’s timeline for decommissioning is significantly later.

  • We will conduct ongoing site maintenance to make sure the site is safe

  • As this is a customer-driven request costs for maintenance are payable by the customer

If you have an existing connection to the NTS and would like to disconnect or decommission it, you will need to follow the A2O process by submitting the physical disconnection form.  

Download the physical disconnection form