Regulation 18 (Investigations) requires a local authority to carry out an investigation where it suspects or has evidence that, a water supply is unacceptable i.e. has or is likely to breach a prescribed concentration or value (PCV) for any water quality parameter specified in the regulations. The purpose of the investigation is to determine the cause of the supply being or likely to be unacceptable and to identify the necessary remedial action(s).
An investigation would usually require a site inspection of the supply and possibly water quality sampling, for example, ingress risks in stored water tanks from animal faeces local the source collection grounds. Other hazards may have developed or changed since the last risk assessment was undertaken and these must be considered too.
If the local authority is satisfied that the cause is due to the pipework (or fittings) within a domestic premise, they must then inform the people concerned promptly. They should give advice on measures necessary steps to restore acceptable quality water. Where water is provided to the public, the local authority must, also inform the appropriate relevant persons that the cause of the unacceptable water is remediated as soon as practicable.
If, after 28 days, the risks have not been mitigated or a suitable plan has not been agreed, the local authority must serve a section 80 notice, (regulation 16(4)(b)) to ensure the improvements are made. Where any relevant person fails to take any remedial steps specified period in the section 80 notice, the local authority may take that step itself and recover expenses reasonably incurred by this action. Local authorities can no longer offer departures from PCVs, as explained in the information note on regulation 19.
If the cause of the water being unacceptable presents a potential danger to human health and the cause is not due to the pipework/distribution system within a domestic premise, the local authority must serve a notice under regulation 20 on the appropriate relevant persons requiring action to be taken.
Where any relevant person specified in a regulation 18 notice fails to take the remedial steps set out in the notice, the local authority may take that step(s) itself. The local authority may recover any expense reasonably incurred by this action.
Regulation 18 also requires that where a parameter that is being monitored on a reduced frequency or is otherwise varied, has breached a PCV, the frequency of monitoring must immediately return to normal frequency following the breach. See guidance note on regulation 7.