Regulation 16 (Regulation 18 (Wales)) requires that whenever there is a failure to meet a standard detected by monitoring or whenever it is suspected for other reasons (e.g. risk assessment, operational incident, compliance sampling) that there could be a failure, the local authority must conduct an investigation to determine the cause.
The investigation has to determine whether the cause of the failure occurred within the private water supplier’s system (raw water, treatment or distribution) or whether it occurred within the pipe work (domestic plumbing and fittings) within premises.
The Regulations also state that once a local authority has completed its investigation and established the cause of the failure, it must take action to restore the water quality so that it is wholesome.
If the local authority cannot secure action within 28 days of finding the cause, it must serve a Notice under Section 80 of the 1991 Act on that person as the relevant person(s).
If, following risk assessment or monitoring, the local authority considers, that a private supply is a potential danger to human health, it must take appropriate steps to ensure that people likely to consume the water are warned and given advice to allow them to minimise any such danger. Furthermore, when any private water supply is a potential danger to human health, the local authority is required to serve a Notice on the relevant person(s) under Regulation 18 (Regulation 20 in Wales) instead of under Section 80 of the 1991 Act