# The Water Supply (Water Quality) Regulations 2018, Regulation 26: Disinfection and other treatment arrangements


(1) Unless the conditions in paragraph (5) are satisfied, before supplying water for regulation 4(1) purposes, a water undertaker or supplementary licensee must—
(a) disinfect the water; and
(b) where necessary, subject the water to sufficient preliminary treatment to prepare it for disinfection.
(2) A water undertaker or supplementary licensee must—
(a) design, operate and maintain the disinfection process so as to keep the presence of disinfection by-products as low as possible without compromising the effectiveness of the disinfection; and
(b) verify the effectiveness of the disinfection process.
(3) Paragraph (4) applies when any property, organism or substance is present in a water source at a level that may constitute a potential danger to human health.
(4) Unless the conditions in paragraph (5) are satisfied, before supplying water for regulation 4(1) purposes using water from any source, a water undertaker or supplementary licensee must design and continuously operate an adequate treatment process for water from the source.
(5) The conditions are that the water undertaker or supplementary licensee —
(a) must supply water from the treatment works as a matter of urgency in order to prevent an unexpected interruption in piped supply to customers; and
(b) before the supply is made, has taken all necessary steps to inform consumers that the water is not disinfected or adequately treated.
(6) For the purposes of this regulation—
(a) “adequate treatment process” means a process of blending or purification treatment which—
(i) Removes; or
(ii) renders harmless the value or concentration of, any property of, organism or substance in, water, so that supplies do not constitute a potential danger to human health;
(b) “sufficient preliminary treatment” means the treatment necessary—
(i) to remove, or to reduce the value or concentration of, any property or substance which would interfere with disinfection; and
(ii) to reduce turbidity to less than one NTU; and
(c) water is supplied for regulation 4(1) purposes when it leaves a treatment works.

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Source: https://www.legislation.gov.uk/wsi/2018/647/regulation/26 (the official version)
Page: https://openlegislation.uk/water-supply-water-quality-regulations-2018/regulation-26
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.