Private Water Supplies - Case Study 2011/07

Change of use of a private supply from a single domestic dwelling to a food premises

This case study relates to a spring supply to a single domestic dwelling. The local authority received a request for advice about water quality from the owners of the property, which at that time was exempt from the monitoring requirements of the regulations. The local authority referred the owner to guidance on source protection available from the Inspectorate and advised about the need to install UV disinfection. However, the owners did not act on this advice. Some time later, the owners informed the local authority of their intention to start a food business and this meant that the private supply fell within the scope of the private supply regulations requiring monitoring and risk assessment (Regulation 9). The initial sample collected contained E.coli therefore the local authority served a Regulation 18 Notice requiring water to be boiled or bottled while an investigation by risk assessment was carried out.

A number of improvements incorporated in the Notice were required to make the supply safe. These included installation of disinfection (UV) with regular maintenance and servicing of the equipment, and the requirement for simple checks or monitoring of the disinfection unit to be carried out, and records kept. Source improvements to prevent contamination from surface and sub surface ingress involved digging a diversion ditch to prevent water entering the supply, raising a storage tank to 150mm above the ground level and fitting a vermin proof cap on the outflow, and clearing vegetation from inside and around the tanks. As part of the annual maintenance the Notice also included cleaning the raw water storage tank by removing vegetation, algae, sediment or debris, disinfecting and flushing the tank and distribution network with chlorine (diluted sodium hypochlorite solution). The local authority, to ensure use of only approved chemicals, provided an advice sheet. The owners cooperated fully and the Notice was revoked once the work was completed, relevant regular checks were in place and a satisfactory verification sample had been obtained. The whole process, from initial sample to completed works and verification, was achieved in approximately six weeks.

This case study illustrates how responsibilities change when a supply to a single domestic dwelling is used for other purposes, for example, a food production business. At this point the local authority must carry out a risk assessment, require the supply to be improved, where necessary, and undertake check and audit monitoring, on the basis of the risk assessment. It should be noted that while the owners had been given access to guidance and general principles about safeguarding the quality of the water supply before setting up the food business, it was only through the process of regulatory risk assessment by the local authority that the owners gained the necessary specific knowledge and understanding of what was required of them to support their business and safeguard public health.