13. In regulation 25 of the 2001 Regulations (treatment of raw water) after paragraph (1) insert—
“(1A) Where the water authority disinfects a supply of water for regulation 4(1) purposes, the water authority shall—
(a)where necessary, subject the water to sufficient preliminary treatment to prepare the water for disinfection;
(b)design, operate and maintain the disinfection process so as to keep disinfection by- products as low as possible without compromising the performance of the disinfection process ; and
(c)verify the performance of the disinfection process.”.