Skip to main content
Search

Wessex Water Services Limited – Tank Inspections

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

Reference: WSX-2026-00001

Version Number: 1

Water undertaker as appointed under section 6 of the Water Industry Act 1991 (as amended): Wessex Water Services Limited, with registered number 02366648 (hereinafter called ‘the Company’).

Assets Affected:

Service reservoirs and treated water storage tanks listed in Annex 1.

Details of this Notice:

  1. The Drinking Water Inspectorate (‘the Inspectorate’) has received a set of regulation 28(1) reports of the Water Supply (Water Quality) Regulations 2016 (as amended) (‘the Regulations’) from the Company dated between 14 July 2025, 5 December 2025 and 11 December 2025 which state that there is or has been a significant risk of supplying water from service reservoirs and treated water storage tanks listed in Annex 1 (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 DMultiple hazard lines e.g.:


Contamination risk


Ingress of contaminants (e.g. surface water; vermin etc)

RSKASMT-0000002430 C001 R66045050RSKASMT-0000009184 H062 T15100637

Contamination risk

Structural deterioration – Dancing hill reservoir

RSKASMT-0000002418 H062 R66045050

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.
  1. 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. Operate all tanks in accordance with current company policy, standards and procedures, that align to recognised standards of good practice.
    Date: Ongoing for the duration of this Notice
  2. Maintain enhanced (in addition to statutory sampling) sampling for any tanks listed in Annex 1. This must include, as a minimum, colony counts, E. coli and coliforms.
    Date: Ongoing for the duration of this Notice
  3. Maintain proactive external site inspections, grounds maintenance, site security and asset maintenance. This must include periodic inspections of hatches, seals, redundant assets, sample taps, overflows, washouts, and air valves.
    Date: Ongoing for the duration of this Notice
  4. Maintain appropriate contingency plans (including liaison with relevant stakeholders as appropriate) to protect human health.
    Date: Ongoing for the duration of this Notice
  5. Keep under review residual chlorine concentrations to ensure appropriate set points and trigger values are in place to prevent a deterioration of drinking water quality.
    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. Complete any enabling works required to isolate the treated water storage tanks to enable inspection and remediation, as listed in annex 1.
    Date: 31 January 2027
  2. Complete an internal inspection of the tanks listed in annex 1.
    Date: 28 February 2027
  3. Complete any remedial works required, before returning the tank to supply.
    Date: 31 March 2027
  4. Develop a risk-based approach to determine the cleaning and physical internal inspection frequency of all Company tanks, to include as a minimum:
  • Time since last inspection
  • Date of construction/age
  • Materials of construction/ tank design
  • Water quality history (to include as a minimum E. coli, coliforms and colony counts)
  • Turnover and tank hydraulics
  • Points of potential ingress (hatches, seals, redundant assets, overflows, washouts, and air valves)
  • Sample tap conditions, tapping points, sample lines and material
  • Any other risks related to individual tanks.
    Date: 30 September 2026
  1. Implement the risk-based approach to cleaning and physical internal inspections of all tanks within the company’s supply area, developed under measure (b)7, ensuring that no tanks exceed the maximum 10-year inspection interval as a maximum.
    Date: 31 May 2027
  2. Identify any treated water storage tanks that will exceed the 10-year maximum interval between inspections.
    Date: Annually by 30 April

(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: 31 July 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 the tanks listed in Annex 1, 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. Submit a list of any newly identified tanks to be included in Annex 1, as required under measure (b)6.
    Date: Annually by 31 May
  3. Confirm the isolation for inspection, all treated water storage tanks listed in annex 1.
    Date: 28 February 2027
  4. Confirm the completion of inspection and any necessary remediation of the treated water storage tanks listed in annex 1 (as required by measure (b)2 and (b)3 respectively).
    Date: 30 April 2027
  5. Outline the risk-based approach developed under measure (b)4.
    Date: 31 October 2026
  6. Confirm implementation of the risk-based approach (measure (b)5).
    Date: 30 June 2027
  7. Submit the audit strategy for auditing the effectiveness of the measures, as specified in measure (c)1.
    Date: 30 August 2026
  8. Submit any revisions of the audit strategy produced under measure (c)2.
    Date: Within 1 month of a revision
  9. 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
  10. Submit a satisfactory completion report accompanied by a revised regulation 28(1) report with Board level Director sign-off.
    Date: 30 June 2027

Further Details of this Notice:

  1. Any product or substance used as a result of the requirements in this Notice must comply with regulation 31.
  2. 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.
  3. 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
29 June 2026
Reference: WSX-2026-00001 v1

Annex 1


Asset


Deadline for completion of enabling works


Deadline for completion of Inspection


Deadline for completion of any remedial works, before return to supply

Cherhill Treatment Works Balance Tank

31 October 2026

30 November 2026

31 January 2027

Dancing Hill New Service Reservoir 1

31 January 2027

28 February 2027

31 March 2027

Table 2: List of treated water storage and chlorine contact tanks that have not been physically internally inspected within the last 10 years.
Back to top
Print page