Trunk water mains review

Last reviewed:

After a series of bursts on our trunk water main network in 2016, we committed to undertake an independent Forensic Review and a Trunk Mains Strategic Review. Below is a summary of what happened, the findings of the reviews, and what we are going to do next.


Trunk water mains have been described as the 'motorways' of the water network. They are large pipes (18" diameter or larger) and carry significant volumes of water at high pressure.

We suffered eight separate bursts on our trunk main network towards the end of 2016. These caused significant damage to homes and businesses, traffic disruption, and temporary loss of water supply.

We're extremely sorry customers were flooded and lost their water supply. We understand how upsetting and disruptive this has been - it was caused by our pipes and it is our responsibility to put everything right.

Our immediate response to the bursts

Our main priority after any burst is to get people’s lives and businesses back to normal as quickly as possible.

We're doing everything we can to repair the damage that was caused as a result of the bursts and to minimise the risk of any future burst mains on our water supply network.

We'll continue to keep in close contact with those directly affected for as long as they need us. We're also committed to ensuring we play our part in engaging with the wider local community moving forwards.

The forensic review

Our Chief Executive, Steve Robertson ordered an immediate forensic analysis of all our trunk main bursts in the last 12 months. The independent Forensic Review was led by Paul Cuttill OBE, a leading voice in the utility sector. Paul has over 30 years’ experience in utilities, including as EDF Power Networks’ Chief Operating Officer.

Specifically the review covered:

  • Causes of each burst – asset condition, its location and environment, and whether any patterns of failure could be identified
  • Impact – on customers, the wider community, and the cost
  • Our immediate response – identifying what we and others did well and what we need to improve
  • Network – whether we need to make changes to network configuration, pumping and control regimes

We have summarised the key findings from the Forensic Review below:

  • There is no single common cause of the bursts. Whilst age and condition of the pipes is an underlying factor in the eight high-profile failures, there were no systematic failings that could be said to have consistently caused or enabled the bursts.
  • There is a clear investment strategy and plan for our trunk mains that is supported by advanced risk and statistical modelling – the Forensic Review recommends that we improve understanding of our network and improve how we manage our existing data and knowledge.
  • The ‘building blocks’ necessary to deliver our trunk water main plans and commitments are in place – the Forensic Review recommends that we focus on improving the management of our planned works and make better use of local knowledge.
  • On improving how we monitor our trunk water mains and spot potential future bursts, the Forensic Review recommends that we accelerate the roll-out of monitoring units (equipment that can monitor where bursts may happen or have already occurred), refresh how we prioritise alarms, increase our capacity to analyse data, and work with partners to develop new, innovative ways of assessing the condition of our pipes.
  • The Forensic Review makes a number of recommendations for improving communication with both customers and within the company immediately after bursts have happened, our capacity to deal with multiple major incidents, and how we can better learn from incidents after they’ve taken place.

The strategic review

The Trunk Mains Strategic Review builds on the recommendations of the preceding independent ‘Forensic Review’. The Strategic Review makes 15 commitments, across five key areas:

  • our operating model;
  • monitoring;
  • asset information;
  • risk management and
  • event response.

We will deliver the 15 commitments from our Strategic Review through an implementation phase over the next 18 months.

Next steps

Significant improvement steps have already been taken. We're already committed an additional £97m investment into our trunk main network over and above what was in our business plan for 2015 to 2020 and we have set aside additional money to support the trunk mains implementation phase, which we will deliver over the next 18 months.

We will continue to work with partners to deliver on the investment with minimal disruption, engaging with our customers throughout.