Concentrationof residual chlorine in drinking water distribution networks Semarang municipal waterworks BSB Jatisari residential service area not meet quality standards. Purpose of this research is to determine the residual chlorine concentration in each node and to know the effect of distance of the reservoir to the consumen to consentration of residual chlorine.
This research used waternet 2.1 software and quantitative descriptive analysis method, where waternet 2.1 software used water quality analysis, quantitative analysis used correlation and regression analysis, while the descriptive analysis are described with tables and graphs. Reasons for the used waternet 2.1 software is the number of pipeline more provided and more complete analysis facilities than previous versions. The independent variable used is the distance distribution (the distance the reservoir to the consumen), while the dependent variable is the concentration of residual chlorine.
The result of the research, the residual chlorine at the nearest node the injection pump is 1.19 mg / l, while at the farthest node is 0.27 mg / l. The results showed the water in the drinking water distribution network Semarang municipal waterworks of BSB service area has a temperature 26 °C with an average pH of 6-7 and do not contain MPN Coliform and E. Coli.
Results of research also indicate that there is a negative relationship between the distance of the reservoir to the consumen with the concentration of residual chlorine, which further increases distance the reservoir to the consumen, then the concentration of residual chlorine will decrease. This relationship has a correlation is not strong, it means there are other factors that also influence. Such factors are flow rate, flow velocity, dimeter pipes and pipe wall roughness coefficient. Obtained from the calculation of regression equation y = -0,002x+1,17, it means every the distance of the reservoir to the consumen increase 1 meter, the concentration of residual chlorine will be reduced 0.002 mg / l. Thus, the concentration of residual chlorine will be exhausted within 585 meters of the reservoir.

Keywords: residual chlorine, distance distribution, municipal waterworks, waternet 2.1