21. Each enforcing authority, in relation to a supply of water, must ensure that—
(a)a failure of the water to meet a parametric value in Table A, Table B or Table C is immediately investigated in order to identify the cause, and assessed to determine whether the failure poses a risk to human health which requires remedial action;
(b)if, for any reason, the supply of water poses a potential danger to human health—
(i)remedial action is taken as is necessary to protect human health (including, where appropriate, action to prohibit the supply of water or to restrict its use); and
(ii)consumers are informed promptly of the danger and given the necessary advice; and
(c)subject to regulation 22, remedial action is taken as soon as possible (after any such failure) to restore the quality of the water so that it meets the parametric value, with priority given to enforcement action having regard among other things to the extent to which the parametric value was exceeded and the potential danger to human health.
22.—(1) In the case of a failure to meet a parametric value in Table C, the duty to take action under regulation 21(c) applies only in so far as action is necessary to protect human health.
(2) The duty of an enforcing authority to take remedial action under regulation 21(c) does not apply in relation to a failure referred to in regulation 21(a) (other than a failure to meet a parametric value for radon, tritium or indicative dose) in a case where it can be established by the enforcing authority that the failure was due to a domestic distribution system or its maintenance.
(3) Where paragraph (2) applies and there is a risk that water supplied through or from any part of the domestic distribution system will, at the point of compliance, contain a parameter which exceeds a parametric value in Table A, Table B or Table C, the enforcing authority must ensure—
(a)that appropriate measures are taken to reduce or eliminate the risk, such as—
(i)advising the person who is responsible for the domestic distribution system of any possible remedial action that the person could take to reduce or eliminate the risk; or
(ii)treating the water before it is supplied to the domestic distribution system so that the parametric value in question is not exceeded at the point of compliance; and
(b)that each consumer of the water is—
(i)informed of the risk; and
(ii)advised of any possible additional remedial action that they should take.
23.—(1) The enforcing authority must ensure that, where remedial action is taken in relation to water pursuant to regulation 21(c), consumers of the water and any other person affected, are—
(a)notified of the risk (if any) to human health and the remedial action taken; and
(b)advised of any additional precautionary measures that may be needed for the protection of human health.
(2) The duty to notify consumers in paragraph (1) does not apply if the enforcing authority confirms, by notice to the Drinking Water Quality Regulator for Scotland, that the remedial action was taken in response to a failure to meet a parametric value (other than a failure to meet a parametric value for radon, tritium or indicative dose) which it considers to be trivial.