AbstractBacterial viruses are prevalent in nature. The coliphage counts in any wastewater sample might show very significant diversity in numbers, due to use of variousEscherichia colistrains. In this study coliphage (E. coliB host) coliform, fecal coliform, and fecal streptococci densities were estimated from chlorinated secondary effluent being carried in a 30‐km long pipeline. Comparison of die‐off of the various indicators was performed between controlled and uncontrolled chlorination at slow and fast flow in the pipe. In addition, a swab technique was applied from which a rough estimation of the ratios of coliphage to the other indicators could be made, as well as coliphage to salmonella ratio. The results showed that there was a decrease in coliphage number at higher levels of chlorine residual, and wherever aftergrowth of coliform occurred, the number of coliphage did not cha