Guide to Improvement programmes

Improvements to water quality

If a water company supplies water that does not meet the required standards or other statutory obligation as set out in the Water Supply (Water Quality) Regulations 2000 (and subsequent amendments) (the Regulations), it must investigate the cause of the problem and notify the Inspectorate of its findings. The Inspectorate assesses each notification and determines whether the failure is likely to recur. Water companies may also approach the Inspectorate if they consider that they are likely to fail a required standard or other statutory obligation.

If the Inspectorate considers that the failure is likely to recur, the company must put in place a legally binding programme of work to improve the quality of the water to the required standard. There are four types of legally binding improvement programmes, these are:

  • Undertakings (accepted under Section 19 of the Water Industry Act 1991);
  • Notices (served under Regulation 28(4) of the Regulations);
  • Authorisations (granted under regulation 20 of the Regulations); and
  • Enforcement Orders (served under Section 18 of the Water Industry Act 1991).

Undertakings and Notices are the most commonly used.

Authorisations cannot be granted unless the Inspectorate is satisfied that they do not pose a potential danger to human health. Enforcement orders will be served for European standards where authorisations cannot be granted. Orders must also be served in respect of failures of the standards for Enterococci and E.coli at consumers’ taps and failure to deliver on agreed actions in either an Undertaking or Notice.


Section 18 of the Water Industry Act 1991 (the Act) requires the Secretary of State and the National Assembly for Wales (the Authorities) to take enforcement action for any enforceable provisions that are not trivial and are likely to recur. Enforceable provisions include:

  • the duty to provide wholesome water, which relates primarily to breaches of the water quality standards;
  • the duties or requirements imposed by Parts IV to VIII of the Water Supply (Water Quality) Regulations 2000 Amended 2007 in England and the Water Supply (Water Quality) Regulations 2010 in Wales (the Regulations);
  • The Water Supply Regulations 2010 which introduced Regulation 26(1A) that requires water companies to (a) design, operate and maintain the disinfection process so as to keep disinfection byproducts as low as possible without compromising the effectiveness of the disinfection, namely

        • monitoring, including sampling and analysis;
        • water treatment;
        • the maintenance of records and the provision of information; and
        • the duty to provide information to the Inspectorate under the Water Suppliers (Information) Direction 2009.

The Inspectorate initiates enforcement action for and on behalf of the Authorities. This usually begins with a ‘notice of intention to enforce’ being served on the company when the Inspectorate is satisfied that the contravention in question is not trivial and cannot be classified as unlikely to recur. The company then usually gives an Undertaking, under Section 19 of the Act, to carry out a programme of work to secure or facilitate compliance with the required standard, or other deficiency identified, within an agreed timescale. However if the company does not give an undertaking, or does not comply with the terms of an undertaking, then the Inspectorate may make a provisional or final enforcement order for the purposes of securing compliance. To date few enforcement orders have been made.
The Inspectorate will not initiate enforcement action when a company, after becoming aware of a breach of a regulatory requirement, takes immediate remedial action and demonstrates that compliance has been achieved.


Regulation 27 of the Amendment Regulations 2007 requires water companies to carry out a risk assessment of each of its treatment works (including the water source and catchment) and the connected supply system.  Under regulation 28, a report of each risk assessment must be provided to the Secretary of State (in practice the Drinking Water Inspectorate). The risk assessment methodology used by water companies should be based on the water safety plan approach published by the World Health Organisation (WHO) in the Guidelines for Drinking Water Quality 2004.

Where a water company in its risk assessment report has identified a significant risk of supplying water that could constitute a potential danger to human health, the Inspectorate on behalf of the Secretary of State may, under regulation 28(4), issue a Notice to require the water company to take certain steps to mitigate the risk.  Exceptionally, the Inspectorate may issue a Notice requiring a water company to stop using the water supply until certain actions have been taken.     

Authorisations (Authorised Departures)

The Regulations contain wholesomeness standards that relate to the requirements of the 1998 EC Directive on the quality of water intended for human consumption (98/83/EEC). They also contain wholesomeness standards for national requirements, to reflect the aesthetic quality of the water at consumers’ taps as well as imposing microbiological standards for water leaving water treatment works and in service reservoirs.

Under the Regulations, water companies may apply to the Authorities for authorisation to supply water that is not wholesome, if they have reason to believe that the water is failing or is likely to fail a standard. The application must also be copied to every appropriate local authority, health authority and the relevant Consumer Council for Water customer service committee in the area supplied, who have the opportunity to make representations on the application.

An authorisation may be granted for a maximum period of three years and must set out the steps that a company will take to achieve compliance within three years. The Authorisations must also specify the extent to which the standard may be exceeded during the period. If the Inspectorate considers that it is not possible for the company to achieve compliance within three years (for example if it has to build a new water treatment works) then the company is required to apply for a further departure.

Authorisations can only be granted if the Authorities are satisfied that the extent of the departure from the standard does not constitute a risk to human health. Therefore, Authorisations are not permitted for breaches of the standards for Enterococci and Escherichia coli (E.coli) at consumers’ taps.

Enforcement Orders

The Inspectorate will proceed with an enforcement order for breaches of the standards for Enterococci and E.coli at consumers’ taps.

The Inspectorate will also proceed with an enforcement order if any of the improvement programmes of work are not delivered as agreed between the Company and the Inspectorate, ie Undertakings and Notices.

Further Information

Clarification of the progress reporting requirements (PDF 110KB) due in January 2015 for catchment management undertakings for pesticides, including metaldehyde  has been sent to all water companies.

You can find out more about programmes of work that your water company is carrying out to improve your water quality by contacting your water company or on our website.


Page reviewed: 18 April 2012
Page modified: 30 September 2014

Drinking Water Inspectorate