Service lines: their effect on microbiological quality

Water that stagnates for long periods in distribution system service lines is susceptible to increases in bacteria, which can be reduced by extensive flushing. The influence of service lines on the microbiological quality of drinking water was investigated. The microbial water quality in domestic service lines was found to differ from that in the main pipes of the distribution system. Differences in bacterial counts from the first flush of the service line and from the main pipe were generally more pronounced in service lines located near the plant. After a thorough flushing of the service line, however, tap water quality was found to be equivalent to that in the main pipe. Bacteriological parameters studied were total direct count after acridine orange staining, heterotrophic plate counts, total coliforms, and Aeromonas. Physicochemical parameters measured included temperature, oxidant residual, and total, dissolved, and biodegradable organic carbon. Lead and copper concentrations were determined in the first flush, after flushing the service line,