Duties of the Drinking Water Inspectorate (DWI)

The DWI regulates drinking water quality in Northern Ireland for public and private supplies.

DWI responsibilities

The DWI:

  • assesses drinking water quality against regulatory standards
  • carries out detailed inspections of water sampling and assesses water treatment, distribution policies and practice
  • publishes an annual report on drinking water quality in Northern Ireland. 
  • develops policy and regulation on drinking water issues in association with other Drinking Water Regulators, working to an agreed Framework contained within a UK Memorandum of Understanding
  • deals with events which affect or could affect drinking water quality
  • liaises with the Utility Regulator to promote co-operation
  • Liaises with DfI under a Memorandum of Understanding
  • works alongside other key stakeholders under a partnership agreement
  • has an agreement with UKAS (the United Kingdom Accreditation Service) ensuring that organisations undertaking sampling or testing of drinking water are UKAS accredited

Regulatory Framework

Drinking Water Quality Standards

Drinking water quality is tested for compliance with the regulatory standards. Tests are carried out for a range of substances or organisms known as parameters. A description of each parameter and its prescribed concentration or value can be found in the European and National Drinking Water Quality Standards table.

Information Letters

Information letters are used to notify the water industry and relevant stakeholders of any changes in regulatory matters, guidance or procedures.

Approved Products

Regulation 33, of The Water Supply (Water Quality) Regulations (Northern Ireland) 2017, controls the application and introduction of products and substances in Northern Ireland. The Drinking Water Inspectorate for England and Wales (DWI [E&W]) provides a technical resource to facilitate this approval in the United Kingdom, and holds the current List of Approved Products for use in Public Water Supply in the United Kingdom.

There is a further requirement, in the private water supply regulations, for any newly installed products or substances to be approved for use with drinking water. Details of approved products, used in the provision of a private supply, are available through the DWI [E&W] website.

Useful contacts

For information related to drinking water, please visit the list of organisations and contact details page.

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