Enforcement
The Inspectorate publishes the drinking water quality Legal Instruments on the website under company improvement programmes. Security (SEMD and NIS) legal instruments are considered sensitive and therefore are not published in the public domain. A summary of the Legal Instruments issued in this quarter is below.
| Type of legal instrument | Number | Companies |
|---|---|---|
| Regulation 28(4) Notice relating to risks identified in water safety plans | 74 | Anglian Water (23), Northumbrian Water (11), South East Water (31), Southern Water (2), South West Water (4), Thames Water (2) United Utilities (1) |
| Undertaking accepted under section 19(1) of the Water Industry Act 1991 | 2 | Thames Water, Severn Trent water |
There was a high level of enforcement activity in the first half of the year due to companies notifying the Inspectorate that they would be unable to fully deliver their legal instruments for tank inspections (and repairs where required). The inspectorate’s approach has been to separate tanks that exceed the notice dates into individual site notices. This is a moderate escalation of the enforcement, the alternative being to pursue section 18 enforcement orders. However, the Inspectorate takes water storage asset health seriously and since 2022, we have enforced where the time between asset inspections has exceeded 10 years.
Notices
Of the notices served, 58 of the 74 have been for tanks being removed from company-wide reservoir notices, as follows. Included in this number are those tanks where companies identified that specific engineering solutions would be required to remove the tank from supply. The companies and number of notices each are; Anglian Water (23), Northumbrian Water (3), South East Water (29), South West Water (3) and Southern Water (1).
Whilst it is accepted that some unanticipated delays will occur, particularly when unforeseen engineering challenges present themselves, the expectation is for this to be for 1 or 2 tanks per company. The high numbers of tanks that failed to be delivered within the notice timescale for South East Water and Anglian Water is concerning and possibly indicates wider project management issue, or that those companies have a higher risk appetite with respect to their treated water storage tanks. The Inspectorate shall continue to apply pressure to companies to assess and mitigate their risks associated with treated water storage assets, using enforcement where required.
A regulation 28(4) notice was served on South West Water for discolouration in its Trethurgy water supply zone. The company acknowledge that a 3 inch unlined cast iron main located within the zone is tuberculated and contributory to various consumer water quality complaints relating to discolouration received in; December 2020, October 2022 and September 2024. A regulation 28(4) notice was served to ensure the proposed filter changes, flushing, sampling and mains replacement scheme is delivered to the timescales outlined by the company.
Anglian Water have experienced exceedances of the Prescribed Concentration or Value (PCV) for Clostridium perfringens from samples of water leaving Welton works on five separate occasions in 2024 (February, twice in June, November and December). There has also been a coliform and an E. coli exceedance from Welton works in July 2023, followed by two further coliform detections in August and September 2023, breaching the requirements of regulation 4. The company’s investigations on site have been inadequate and have not satisfied the requirements of regulations 18 and 19, despite the elongated timeframe over which investigations could have been executed to determine a root cause. There is evidence that the performance of the rapid gravity filters cannot adequately show compliance with regulation 26 and the requirements of regulation 27. The notice requires additional, detailed investigation, which will include installation of additional monitors and a sampling programme for Clostridium and other microbiological parameters, to identify potential sources of contamination and the development of a mitigation plan. The company have opted to install ultraviolet treatment at the works. Under the notice, the company are due to deliver improvements before the end of 2025, protecting the wholesomeness of supplies to 50,306 consumers.
Following on from the Inspectorate’s technical audit of Northumbrian Water’s risk management of air valves, several deficiencies were identified, such as issues with the maintenance records, no risk-based inspection frequency, and the lack of clear procedures for all air valve inspections. The Inspectorate therefore served a regulation 28(4) notice upon the company to address the deficiencies identified. The notice covers all raw water impounding reservoirs, raw water mains, treatment works, strategic mains, service reservoirs and distribution mains in water supply zones within the company’s operating area and is due to be completed in March 2028.
A company-wide disinfection improvements notice has been served on Northumbrian Water due to many deficiencies identified during a technical audit of the company’s disinfection policy. In a rare occurrence for the drinking water sector in England and Wales, the company did not to return a completed draft notice or respond formally, following the receipt of a minded to enforce letter and so the notice was served entirely as written by the Inspectorate. The notice requires many factors to be reviewed and the disinfection policy to be updated once all are completed, ultimately ensuring that the disinfection arrangements operated by the company comply to its new standard. The notice is due to complete by the end of 2025 and effectively ensures wholesome supplies to all of the company’s consumers.
Five notices were served on Northumbrian Water for PR24/AMP8 schemes. These were schemes which had not originally been shared with the Inspectorate by the company. Ofwat identified, in its final reviews ahead of publishing its final determination in December 2024, that there were funded schemes with a drinking water quality impact, which the Inspectorate had not been sighted to. The company had initially submitted the schemes to Ofwat as resilience only schemes. On provision of the required information, the Inspectorate assessed there was a drinking water quality impact and supported the schemes. These were formalised as regulation 28(4) notices during the second quarter of 2025 and are summarised in the table below.
Conditional Allowance Schemes
The remaining three schemes were conditional allowance schemes. Thames Water agreed conditional allowances with Ofwat for specific improvements at Coppermills and Hampton water treatment works and at a third site. As with AMP schemes and in line with the principals of Better Regulation, the Inspectorate will track the progress of these schemes and provide feedback to Ofwat on their delivery. The specific schemes are detailed in the following table.
| Affected site | Legal instrument type | Improvements being delivered | Affected population |
|---|---|---|---|
| Coppermills | Regulation 28(4) Notice | Improvements to the High Lift Pumping Station. Design, install and commission a slow sand filter recirculation system, allowing isolation of individual sand filters in case of disinfection failure. Design a permanent contact tank drain-down system. | 2,784,147 |
| Hampton | Regulation 28(4) Notice | Bulk recycle flow (pre-contact tank) to the Grand Junction Reservoir and upgrades to the emergency pumping facilities | 4,699,778 |
| Site 3* | Section 19(1) Undertaking | *This scheme falls under the remit of SEMD and so the details are not published in the public domain. | – |
AMP8 Schemes
During Ofwat’s final checks of its Final Determination, it identified several schemes which the Inspectorate had commended for support, but which were not being monitored by legal instruments or acknowledged actions. The Inspectorate therefore put in place acknowledged actions for these schemes.
| Company | Scheme name | Details |
|---|---|---|
| Anglian Water | Bocking Taste and Odour | To remove chlorine dosing and instead install biological filters and UV disinfection, to mitigate taste and odour risks. The scheme will benefit 55,001 consumers and be delivered by 31 August 2029. |
| Anglian Water | Earls Colne Taste and Odour | For unchlorinated backwash water for filters. This improvement will remove taste and odour issues associated with site, due to biological filters affected by chlorinated back wash water. Installation to be completed by March 2030, benefitting 11,063 consumers. |
| Dŵr Cymru | Bontgoch filter refurbishment | First stage filter improvements to manage increasing raw water solids loading onto the site. This improvement will increase the backwashing capability of the first stage filters during periods of poor raw water quality, benefitting 28,876 consumers. |
| Southern Water | Disinfection Resilience | The original submission included 13 sites, 4 of these were included in R28(4) notices. The remaining nine were commended for support. A mixture of UV installation to protect against Cryptosporidium, hardening existing physical barriers or increasing contact time to enhance virus removal at the sites. Work to take place across AMP8 and be completed by 31 March 2030. |
| Scheme name | Description |
|---|---|
| Barsham Nitrate | The company will install a nitrate treatment plant at Barsham WTW by 30 April 2032. This will protect the supply of wholesome drinking water to 116,040 consumers. |
| Langford Nitrate | The company will install a nitrate treatment plant at Langford WTW by 30 April 2032. This will protect the supply of wholesome drinking water to 367,960 consumers. |
| Langford Clarifiers | The company will complete clarifier improvements at Langford WTW by 30 April 2032. This will protect the supply of wholesome drinking water to 367,960 consumers. |
| Langford UV treatment | The company will install a UV treatment plant at Langford WTW by 30 June 2030. This will protect the supply of wholesome drinking water to 367,960 consumers. |
| Langham Nitrate | The company will install a nitrate treatment plant at Langham WTW by 30 April 2032. This will protect the supply of wholesome drinking water to 991,220 consumers. |
South East Water were served with two additional reservoir inspection notices for Bloodshots reservoir 1 and Stanstead service reservoir. As with Anglian Water, the company have a company-wide notice requiring all reservoirs and other tanks to be inspected at a risk-based frequency, not exceeding 10-years. These two reservoirs have exceeded 10 years between inspections and are in addition to the 29 notices already served during the first quarter of 2025.
Similarly, Southern Water were unable to meet the dates in its company-wide reservoir notice for interstage assets at its Burham works due to interactions with site Final Enforcement Order (FEO), and requirements of enabling works with valves on site. The dates in the new notice, whilst a delay on the original requirements tie in with site shutdowns around FEO dates to enable more efficient project management.
The Inspectorate carried out an audit of United Utilities’ Sutton Hall works in November 2024, as a result of a significant taste and odour event. The Inspectorate identified shortcomings in the company’s management of the filtration and powdered activated carbon treatment stages. Consequently, to address the shortcomings, a notice was served upon the company to implement improvements. The notice will benefit 395,421 people and will be completed by September 2029.
The Inspectorate also varied a notice already served on United Utilities, during the quarter. Huntington water treatment works already had a notice in place, to implement a new start-up-to-waste project and other improvements. The Inspectorate carried out an audit of the works in December 2024, following on from a significant taste and odour event and a bacteriological compliance sample breach. During the audit, the Inspectorate identified shortcomings in the company’s Powdered Activated Carbon (PAC) dosing, filtration maintenance and management, and contact tank inspection philosophy. The Inspectorate therefore decided to vary the existing notice under regulation 28(6), to add further improvement requirements to the notice, to address the deficiencies noted. The improvements will benefit 1,679,511 people and will be completed in September 2029.
Undertakings
Severn Trent Water has given an undertaking to install telemetry upgrades on Boughton (Chester) works. The works is currently unable to store sufficient data from the onsite, electronic monitoring, where carried out for regulatory purposes. This is in contravention of regulation 34(1). All actions are due to be completed by the end of June 2027 and will help to ensure wholesome supplies to the 104,367 consumers supplied by this water treatment works.