§ 109.710. Disinfectant residual in the distribution system.

 (a)  A disinfectant residual acceptable to the Department shall be maintained throughout the distribution system of the community water system sufficient to assure compliance with the microbiological MCLs and the treatment technique requirements specified in §  109.202 (relating to State MCLs, MRDLs and treatment technique requirements). The Department will determine the acceptable residual of the disinfectant considering factors such as type and form of disinfectant, temperature and pH of the water, and other characteristics of the water system.

 (b)  A public water system that uses surface water or GUDI sources or obtains finished water from another permitted public water system using surface water or GUDI sources shall comply with the following requirements:

   (1)  As a minimum, a detectable residual disinfectant concentration of 0.02 mg/L measured as total chlorine, combined chlorine or chlorine dioxide shall be maintained throughout the distribution system as demonstrated by monitoring conducted under §  109.301(1) and (2) or (8)(v) (relating to general monitoring requirements).

   (2)  Sampling points with nondetectable disinfectant residuals which have heterotrophic plate count (HPC) measurements of less than 500/ml are deemed to be in compliance with paragraph (1).

   (3)  When the requirements of paragraph (1) or (2) cannot be achieved, the supplier shall initiate an investigation under the Department’s direction to determine the cause, potential health risks and appropriate remedial measures.

 (c)  Public water systems may increase residual chlorine or chloramine, but not chlorine dioxide, disinfectant levels in the distribution system to a level that exceeds the MRDL for that disinfectant and for a time necessary to protect public health or to address specific microbiological contamination problems caused by circumstances such as, but not limited to, distribution line breaks, storm runoff events, source water contamination events or cross-connection events.

   The provisions of this §  109.710 adopted December 7, 1984, effective December 8, 1984, 14 Pa.B. 4479; corrected December 14, 1984, effective December 8, 1984, 14 Pa.B. 4511; amended March 24, 1989, effective March 25, 1989, 19 Pa.B. 1289; amended May 15, 1992, effective May 16, 1992, 22 Pa.B. 2621; amended July 20, 2001, effective July 21, 2001, 31 Pa.B. 3895 and 3938; amended August 13, 2004, effective August 14, 2004, 34 Pa.B. 4435. Immediately preceding text appears at serial page (290569).

   This section cited in 25 Pa. Code §  109.701 (relating to reporting and record keeping).