25.—(1) A water undertaker shall not, otherwise than for the purposes of testing or research, apply any substance or product to, or introduce any substance or product into, water which is to be supplied for drinking, washing and cooking unless–
(a)the Secretary of State has for the time being approved the application or introduction of that substance or product and it is applied or introduced in accordance with any conditions attaching to that approval; or
(b)the undertaker is satisfied that the substance or product either alone or in combination with any other substance or product in the water is unlikely to affect the quality of the water supplied; or
(c)the undertaker can demonstrate that the substance or product has during the period of twelve months preceding the making of these Regulations been applied or introduced (otherwise than for the purposes of testing or research) by a water authority or a statutory water company into water supplied by it for domestic purposes; or
(d)the substance or product–
(i)was at any time before the commencement of these Regulations listed in the 15th Statement of the Committee on Chemicals and Materials of Construction for Use in Public Water Supply and Swimming Pools(1) or in any supplement to that Statement issued before the making of these Regulations; and
(ii)is applied or introduced in accordance with any conditions referred to in that Statement or any supplement so issued or any such conditions as varied under paragraph (5) of this regulation and any conditions imposed under that paragraph.
Sub-paragraphs (b) to (d) have effect subject to paragraph (4) below.
(2) An application for such an approval as is mentioned in paragraph (1)(a) may be made by any person.
(3) The Secretary of State may, if he decides to issue an approval for the purpose of paragraph (1)(a), include in the approval such conditions as he considers appropriate and, subject to paragraph (6), may at any time revoke or vary any approval he has previously given.
(4) The Secretary of State may by notice given in writing to any water undertaker prohibit it for such period as is specified in the notice from applying to, or introducing into, water intended to be supplied for drinking, washing and cooking any substance or product which the undertaker would otherwise be authorised to apply or introduce by paragraph (1)(b), (c) or (d).
(5) The Secretary of State may by notice in writing to water undertakers vary any condition contained in the 15th Statement or any supplement referred to in paragraph (1)(d)(i) or impose conditions as to the application or introduction of any substance or product listed in that Statement or any supplement.
(6) The Secretary of State may–
(a)revoke by an instrument in writing any approval given by him for the purposes of paragraph (1)(a);
(b)modify any such approval by an instrument in writing by including conditions, or varying existing conditions;
(c)issue any such notice as is mentioned in paragraph (4):
but, unless he is satisfied that it is necessary to do so in the interests of public health without notice, shall not do any of those things without giving all such persons as are, in his opinion, likely to be affected by the revocation or modification of the approval or by the issue of the notice at least six months' notice in writing of his intention.
(7) Notice shall be given forthwith by the Secretary of State to all persons likely to be affected by the making of such an instrument as is mentioned in paragraph (6)(a) or (b).
(8) At least once in each year beginning with the year 1990, the Secretary of State shall issue a list of all the substances and products in relation to which–
(a)an approval for the purposes of paragraph (1)(a) has been granted or refused;
(b)such an approval has been revoked or modified;
(c)a notice has been issued under paragraph (4),
with particulars of the action taken.
The 15th Statement was issued in March 1989. Copies of it and of any supplement may be obtained from the Department of the Environment, Romney House, 43 Marsham Street, London SW1P 3PY.