Guidance documents

Regulation 5

The purpose of Regulation 5 is to prevent the use of products or substances being used within a private water supply system that may have a detrimental effect on the safety or quality of drinking water. Any product used within such a system must have documentation demonstrating that prior to use checks were undertaken to ensure that the product or substance conforms to the requirements of this Regulation.

The Inspectorate has published a letter (reference 01/2022) on updated guidance of Regulation 5.

The updated guidance on Regulation 5 is found here:



Approving a Product

If a product or substance has gained Regulation 5 approval then it will be included in the list of approved products. In order for a product/substance to be included on this list then the manufacturer or supplier must be able to show that the product or substance has been used, in at least three different private water supplies for a period of 12 months, prior to the date of application

To apply for Regulation 5 approval then a Regulation 5 Application form will need to be completed and returned to DWI:

Regulation 5 Application form