Water quality in distribution systems has become a prominent issue in the study of water networks. This study concentrates on chlorine disinfection as an indicator of water quality. The model discussed in this work is based on laboratory and field collected data. The model is applied on a real network which exists in Almonsha city in Upper Egypt. The experimental set-up and procedure of measuring bulk (Kb) and wall (Kw) chlorine decay coefficients are described. The collected field data together with experimental results are used for calibrating the model using extended period simulation. The aim of this study is to find a solution for the absent of the free residual chlorine in several sections of Almonsha water distribution network. The diurnal variations of domestic water consumption are taken into consideration. Also, different values have been assigned for the daily water consumption for both rural and urban zones of the network. Different water resources (surface and underground water) have been involved in the model. Underground water reservoirs and high elevated tanks are included in the simulation. The water level in the high elevated tanks and water table in the feeding wells are studied. The free residual chlorine concentrations (FRCCs) were measured at different sections of the network and used for the model calibration. FRCCs have been simulated in different locations of the network at several times using extended period simulation. The results of the field and experimental works have shown that, the initial chlorine concentration (C0) has an effect on Kb, an equation is derived to express the relation between them. Also, another equation is derived for the relation between C0 and Kw. The simulation process was extended for several months to dispose the effect of the initial conditions. It is found that, with the existing system of chlorine injection, some parts of the network keep nil values of FRCC even with an injected free residual chlorine dose reaching to 5 mg/L at the feeding point. A new technique is proposed. This technique is based on superposition method for chlorine disinfection. Finally, with the superposition method, it is found that, the minimum injected chlorine dose which should be injected at the feeding points ranges between 0.83 mg/L to 2 mg/L. This dose is found to be sufficient to keep the minimum FRCC with values not less than 0.3 mg/L for the whole parts of the concerned network at all day hours