While substantial quantities are required to effectively disinfect large diameter wells, it can be easily mixed with the water and it is relatively safe to handle and use. Like sodium hypochlorite, it slowly loses its strength with exposure to air and should be stored in sealed containers in a cool dark place to retain its strength.
Chlorine is a very reactive substance.
However, it is slow acting and long contact times are required. Generally HCl doesn't become a problem in the desired pH range of drinking water. In addition, chlorine is a surface-active agent and, since it can not effectively penetrate solids to kill concealed bacteria, disinfection of turbid water will be incomplete. Finally, it is difficult to achieve even mixing of chlorine and water in large diameter wells, chlorine tends to settle to the bottom of wells and high chlorine concentrations must reach the outside of the well tiles and the surrounding gravel pack. As a result, much higher chlorine doses are required for shock chlorination of wells than are used in operating treatment systems.