Abstract: One of the most important disinfectants is being considered chlorine for its wide and moderate availability in most areas of the world. The presence of chlorine in different areas of the system is very important to ensure the occurrence of water disinfection. The research goals aimed to find the residual chlorine concentration in the water outside and inside the chlorine basin of Al-Tayyara water treatment plant in Babylon, Iraq. Some of its supplied water to the regions such as (Al-Tayyara and Abi-Gharaq) in Babylon which represent the first and the last region are equipped with water from Al-Tayyara water treatment plant. pH, temperature, turbidity and some important water properties Ca, TDS and EC are also measured during January and February. The results showed that residual chlorine concentration ranged from 0.29-2.3 mg/L. Most of the residual chlorine concentrations were obtained higher than the maximum permissible limit according to the Iraqi standers No. 417, 2001. The other properties were within the permitted level by the Iraqi standers.