(cache)Enforcement case into Wessex Water's management of its sewage treatment works and sewerage network

In March 2022 we opened an enforcement investigation into Wessex Water to investigate whether it was managing its wastewater treatment works and networks appropriately, such that the company limits spills and environmental harm from storm overflows.

This case is part of a wider investigation Ofwat has into all water and wastewater companies in England and Wales on this topic. For further detail about this investigation, how it has developed and the legal obligations being considered please see investigation into sewage treatment works.

On 11 November 2025, we published a consultation, setting out the findings of our investigation and our proposal to accept undertakings provided by Wessex Water under section 19 of the Water Industry Act 1991 (WIA91), in lieu of us imposing an enforcement order and penalty on the company. The undertakings set out details of the steps Wessex Water will take to address the non-compliance we identified and secure future compliance with its obligations. The undertakings also set out details of a proposed redress package valued at £11m to recognise the failures our investigation found. On 16 December 2025, we published our final decision for this case.

Summary of Ofwat’s decision

We have concluded that Wessex Water has contravened:

Regulation 4(4), Regulation 4(2) and Schedule 2 of the Urban Waste Water Treatment (England and Wales) Regulations 1994 (UWWTR) by failing to operate and maintain its wastewater assets adequately, and to upgrade them where necessary, to provide sufficient performance. It has also failed to put in place adequate processes and systems to routinely monitor and maintain the capacity and performance of its assets to ensure they were meeting legal requirements.
Section 94 WIA91 by systemically contravening its UWWTR duties and failing effectually to provide drainage and deal with the contents of its sewers.
Condition P12 of its licence, which requires it to have in place adequate resources and systems of planning and internal control to carry out its legal obligations, by failing to put in place adequate processes to effectively identify and address emerging and present compliance risks; to ensure that its data gathering and analysis were fit-for-purpose; and to ensure that its Executive and Board received and/or sought sufficient information and assurance on the company’s operational performance.

We received no responses to the consultation and remain satisfied that the undertakings proposed by Wessex Water will secure the company’s compliance. We have therefore decided to accept the undertakings. As a result, our duty to impose an enforcement order to secure compliance falls away.

We have also concluded that it would be appropriate to accept the undertakings in lieu of the financial penalty we would otherwise impose in this case (£10 million, 2.5% of the company’s relevant turnover). The redress package within the undertakings will be entirely funded by the company and its shareholders, rather than customers.

The £11 million redress package will deliver a better outcome for customers and the environment by means of:

Creating a £1.1 million Rainwater Management Fund that will support customers in managing rainwater sustainably at their properties, providing grants and expert support to prevent rainwater entering combined sewers and reducing potable water use, thereby reducing customer bills.
A £1.3 million investment in installing flow monitors at 133 sites, covering costs that would otherwise have been funded by customers under the price review.

The remaining £8.6 million will be allocated between:

Engaging with private landowners and investing in sealing privately owned drains and sewers on private land in order to reduce the level of infiltration into the company’s own network.
Investing to reduce spills at specific storm overflows. This investment is additional to that the company already has planned for 2025-30 through the price review and relates to storm overflows that were not previously scheduled for improvement until after 2030.

The undertakings are enforceable by us under section 18 WIA91 and we will monitor Wessex Water’s delivery of them. Wessex Water has also committed to publishing on its website details of its progress and a summary of the actions it has taken.