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 2016 (and subsequent amendments) in England or the Water Supply (Water Quality) Regulations 2018 in Wales (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 Inspectorate may require the company to put in place a legally binding programme of work to improve the quality of the water to the required standard. There are three main types of legally binding improvement programmes (legal instruments), these are:

  • Notices, served under Regulation 28(4) of the Regulations;
  • Undertakings, accepted under Section 19 of the Water Industry Act 1991 (as amended);
  • Enforcement Orders, served under Section 18 of the Water Industry Act 1991 (as amended).

Notices are the most commonly used and are linked directly to risk assessments carried out the by the water companies.

Undertakings are used less often and generally reserved for situations where a company are at risk of non-compliance for a matter not covered by a risk assessment. An undertaking can also be offered by a water company if they apprehend a potential to breach the requirements and they commit to deliver a legally binding improvement program to prevent the risk being realised.

Orders are rarely used but are considered for use where the failures are of a serious nature, or if a company fails to deliver on agreed actions in either an Undertaking or Notice.

Enforcement usually begins with a ‘minded 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 type of legal instrument used depends on the particular circumstances, but usually a Notice under Regulation 28(4) will be used. Commonly, the Inspectorate will send the company a Notice template which they will complete to specify a program of work to mitigate the risks present, within an agreed timescale.

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 and the risk(s) mitigated.


Regulation 27 of the Regulations 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 or Welsh Ministers (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.

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 issue a Notice to require the water company to take certain steps to mitigate the risk under Regulation 28(4).  Exceptionally, the Inspectorate may issue a Notice requiring a water company to stop using the water supply until certain actions have been taken (prohibition of supply). 


Section 18 of the Water Industry Act 1991 (as amended) (the Act) requires the Secretary of State and the Welsh Ministers (the Authorities) to take enforcement action for any enforceable provisions that are not trivial and are likely to recur. In this capacity, the Drinking Water Inspectorate act on behalf of the Secretary of State and Welsh Ministers. As previously stated, undertakings are generally used where a Notice under Regulation 28(4) cannot be used, i.e. there is no appropriate risk assessment.

Enforcement Orders

The Inspectorate will proceed with an enforcement order for serious breaches of the Regulations, or for serious issues which are not enforceable under Regulation 28(4) of the Regulations.

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

Further Information

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.

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