Severn Trent Water Limited – Discolouration

Notice under regulation 28(4) of the Water Supply (Water Quality) Regulations 2016 (as amended)

Reference: SVT-2026-00021

Version Number: 1

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Severn Trent Water Limited, with registered number 02366686 (hereinafter called ‘the company’).

Assets Affected:

• Water Supply Zones listed in Annex 1

Details of this Notice:

1. The Drinking Water Inspectorate (‘the Inspectorate’) has received a regulation 28(1) report of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the company on various dates between 2024 and 2026, which states that there is or has been a significant risk of supplying water from multiple sites (and associated assets as applicable) that could constitute a potential danger to human health or could be unwholesome.
2. Consequently, this Notice is served on the company by the Inspectorate on behalf of the Secretary of State, under regulation 28(4) for the assets listed above, for risks associated with:

Description of Risk	Hazard/ Hazardous Event/ Parameter	Hazard I D example from Cookley WSZ
Consumer acceptability (discolouration)	Iron	ZWC06-4776-D-A022-A022-01A
Consumer acceptability (discolouration)	Turbidity	ZWC06-4776-CO-H057-A002-004
Consumer acceptability (discolouration)	Manganese	ZWC06-4776-D-A023-A023-01C
Consumer acceptability (discolouration)	Aluminium	ZWC06-4776-CO-A021-A021-02F
Consumer acceptability (discolouration)	Discolouration	ZWC06-4776-CO-H057-H057-AAA

Table 1: Table of the hazards, hazardous events, and/or parameters covered by this Notice, including the Hazard I D numbers and the description of risks.

3. The company are required to satisfy the following requirements.

The date given is that until or by which the requirements must be maintained or satisfied, as appropriate.

Requirements:

(a) To maintain the following measures for the period specified in each case:

1. Undertake enhanced monitoring as defined within section (c)1 from water supply zones in Annex 1.
   Date: Ongoing for the duration of this Notice
2. Optimisation of existing treatment processes to reduce manganese, iron, aluminium in the final water as low as possible at all water treatment works.
   Date: Ongoing for the duration of this Notice
3. Investigate any failure of a discolouration parameter (aluminium, iron, manganese or turbidity) and determine root cause.
   Date: Ongoing for the duration of this Notice
4. Record and monitor customer contacts in appropriate detail, and along with water quality data, keep under review to informthe forward programme of work.
   Date: Ongoing for the duration of this Notice
5. Training of staff and third-party contractors to facilitate more effective network operation and management and minimise disruption to customer supplies through Company’s activities.
   Date: Ongoing for the duration of this Notice
6. Follow and implement industry good practice methodologies where appropriate. Benchmark the Company’s discolouration strategy against other water companies. Review at regular Discolouration Steering Group meetings.
   Date: Ongoing for the duration of this Notice
7. Adequate risk assessment planning, with appropriate sign-off, before completion of any planned work in order to consider and reduce the risk of customer impact.
   Date: Ongoing for the duration of this Notice

(b) To review, revise or make operational the following measures, by the dates specified in each case:

1. Develop a Company discolouration strategy to reduce the risk of discoloured water in water supply zones, which is benchmarked against industry good practice.
   Date: 31 December 2026
2. Review and update procedures for investigation consumer contacts for discolouration, sample failure for discolouration parameters (iron, manganese, aluminium and turbidity) and water quality discolouration events, including cluster analysis and hotspots.
   Date: 30 September 2026
3. Develop a dynamic risk assessment methodology for water supply zones, utilising all relevant sources of data and with input from relevant stakeholders, to prioritise zones for further investigation and remedial work to reduce the risk of consumer contacts regarding discoloured water. To include;
   • Treatment works
   • Service Reservoirs
   • Trunk mains
   • Zonal network
     Date: 31 December 2026
4. Review discolouration data from all sources and complete risk assessments for all zones. Update regulation 28 report where necessary. Categorise into Low, Medium and High-risk zones. 
   Date: 31 December 2026, then annually by 30 June
5. Develop a discolouration root cause analysis methodology to understand the reasons for discolouration, utilising all relevant sources of data, with input from relevant stakeholders. 
   Date: 31 October 2026
6. Undertake a root cause analysis for the zones identified as high and medium risk within (b)4, to understand discolouration within the zones. Identify bespoke solutions for each zone.
   Date: a) by 31 January 2027 for high-risk zones.
   Date: b) by 31 March 2027 for medium risk zones
   Date: c) by 30 June annually for new high and medium risk zones for the duration of the notice.
7. Using the outputs from the root cause analysis in (b)6 and risk assessment in (b)4 develop a detailed plan with timescales for all high and medium risk zones to reduce the risks of discolouration to consumers. This should be specific to each zone and include;
   • Treatment works optimisations
   • Service reservoir risk assessment and cleaning
   • Work on trunk mains and pumping stations
   • Water quality zones and DMAs
     Date: 30 April 2027 for high risk zones
     Date: 30 June 2027 for medium risk zones
     Date: Annually by 30 September for any new high and medium risk zones for the duration of the notice
8. Implement bespoke solutions as identified in (b)7, prioritising zones with a higher risk of discolouration, consumer contacts and consumer acceptability to achieve the following;
   • Reduction in discolouration contacts to a company average of 0.3 per 1000 population regionally. Any zones with a contact rate above (0.94 per 1000 population) to be included in Annex 1.
   • Maximum discolouration contact rate of 0.94 per 1000 population for individual zones.
     Date: 31 March 2030
9. Document all optimisation that has been carried out as part of (a)2 at treatment works to minimise discolouration and identify outstanding actions with timelines.
   Date: Annually by 31 January for the duration of the notice

(c) To audit whether the measures have been effective by the following means:

1. Define an audit strategy to monitor the effectiveness of the measures specified in sections (a) and (b).
   Date: 6 September 2026
2. Implement, and keep under continuous review, the audit strategy defined in measure (c)1.
   Date: Following completion of measure (c)1. onwards.

(d) Not to supply water for regulation 4(1) purposes from multiple zones, or not to so supply unless the specified conditions below are satisfied:

1. Not applicable

(e) To provide the following information in the time and manner specified below to enable monitoring of progress towards the mitigation of the risks:

1. Provide a progress report annually.
   Date: by 31 January each year.
2. Provide a report on the Company discolouration strategy as required in (b)1.
   Date: 31 January 2027
3. Provide a report on the procedural updates, required in (b)2
   Date: 31 October 2026
4. Provide a report on the dynamic risk assessment methodology as detailed in (b)3.
   Date: 31 January 2027
5. Provide a report on (b)4, including a list of zones categorised into low, medium or high-risk.
   Date: 31 January 2027, then annually by 31 July for the duration of the notice.
6. Provide a report on the discolouration root cause analysis methodology, as detailed in (b)5.
   Date: 30 November 2026
7. Provide a report as described in (b)6 on the root cause analysis for the high and medium risk zones, include the bespoke solutions for each zone.
   Date: a) by 28 February 2027 for high-risk zones.
   Date: b) by 30 April 2027 for medium-risk zones.
   Date: c) by 31 July annually for new high and medium risk zones for the duration of the notice.
8. Provide a report on the detailed plan with timescales as required in (b)7.
   Date: a) by 31 May 2027 for high-risk zones.
   Date: b) by 31 July 2027 for medium-risk zones.
   Date: c) by 31 October annually for new high and medium risk zones for the duration of the notice.
9. On an annual basis provide a report on progress made on (b)8, to implement the bespoke solutions.
   Date: Annually by 30 April
10. Provide a report with evidence detailing which high or medium risk zones have had successful work undertaken where they no longer meet the criteria (0.94 per 1000 population criteria). Any zones that have met this requirement and have had an updated Regulation 28(1) risk assessment may be removed from Annex 1. This report should include information on the measures taken to manage and reduce the risk of discolouration along with an independent assessment of actions and results.
    Date: Annually by 30 April
11. Provide a report on progress made as detailed in (b)9 on WTW optimisation and outstanding actions.
    Date: Annually by 28 February
12. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: 6 October 2026
13. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
14. Submit a report in the event that any completed measures of this Notice need to be altered in any way, for any reason.
    Date: Ongoing for the duration of this Notice
15. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 30 April 2031

Further Details of this Notice:

4. Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
5. Under regulation 28(6) the Inspectorate, on behalf of the Secretary of State, may by notice served on the company, revoke or vary this Notice.
6. Failure by the company to comply with this Notice may result in enforcement proceedings under section 18 of the Water Industry Act 1991 (as amended).

Signed

 

Nicholas Adjei
Deputy Chief Inspector, on behalf of the Secretary of State for Environment, Food and Rural Affairs
6 July 2026
Reference: SVT-2026-000021