4.—(1) Water supplied—
(a)for such domestic purposes as consist in or include, cooking, drinking, food preparation or washing; or
(b)to premises in which food is produced,
shall, subject to paragraphs (4) and (5), be regarded as wholesome for the purposes of Chapter III, as it applies to the supply of water for those domestic purposes, if the requirements of paragraph (2) are satisfied.
(2) The requirements of this paragraph are—
(a)that the water does not contain—
(i)any micro-organism (other than a parameter) or parasite; or
(ii)any substance (other than a parameter),
at a concentration or value which would constitute a potential danger to human health;
(b)that the water does not contain any substance (whether or not a parameter) at a concentration or value which, in conjunction with any other substance it contains (whether or not a parameter) would constitute a potential danger to human health;
(c)that the water does not contain concentrations or values of the parameters listed in Tables A and B in Schedule 1 in excess of or, as the case may be, less than, the prescribed concentrations or values;
(d)that the water satisfies the formula [nitrate]/50 + [nitrite]/3 ≤ 1, where the square brackets signify the concentrations in mg/1 for nitrate (NO3) and nitrite (NO2).
(3) The point at which the requirements of paragraph (2), in so far as they relate to the parameters set out in Part I of Table A and in Table B in Schedule 1 are to be complied with is—
(a)in the case of water supplied from a tanker, the point at which the water emerges from the tanker;
(b)in any other case, the consumer’s tap.
(4) Water supplied for regulation 4(1) purposes shall not be regarded as wholesome for the purposes of Chapter III if, on transfer from a treatment works for supply for those purposes—
(a)it contains a concentration of the coliform bacteria or E. coli parameter (items 1 and 2 in Part II of Table A in Schedule 1) in excess of the prescribed concentrations; or
(b)it contains a concentration of nitrite in excess of 0.1mgNO2/1.
(5) Subject to paragraph (6), water supplied for regulation 4(1) purposes shall not be regarded as wholesome for the purposes of Chapter III if, on transfer from a service reservoir for supply for those purposes, it contains a concentration of the coliform bacteria or E. coli parameter in excess of the prescribed concentrations.
(6) Water transferred from a service reservoir for supply for regulation 4(1) purposes shall not be regarded as unwholesome for the purposes of Chapter III because the maximum concentration for the coliform bacteria parameter is exceeded if, as regards the samples taken in any year in which the reservoir in question is in use, the results of analysis for that parameter establish that in at least 95 per cent of those samples coliforms were absent.