The Water Supply (Water Quality) Regulations 1989

Sampling—additional samples

19.—(1) If, as a consequence of any change in a water undertaker’s practices in treating water at a treatment works or service reservoir, the undertaker is of the opinion that the prescribed concentration or value in respect of any parameter mentioned in Tables 1 to 5 has been or may be contravened, it shall until the end of the next following year (or for such other period as the Secretary of State may notify to the undertaker in writing) take for analysis for testing for compliance with that parameter the number of samples specified in paragraph (2).

(2) The number of samples to be taken is–

(a) for any whole year in the period, the increased corresponding number specified in the relevant Table for that parameter or (where none is specified) the standard number;

(b) for any other period, the appropriate increased corresponding number multiplied by the number of whole months in the period and divided by 12; and, where the result is not a whole number, rounded upwards to the nearest whole number.

(3) Where an analysis of samples taken in accordance with paragraph (1) demonstrates that there has been no contravention of the prescribed concentration or value in the relevant period, the undertaker may revert to sampling in accordance with regulation 13(1).