In order to safeguard the public against waterborne diseases, water utilities must secure that multiple, microbial barriers are provided for in their drinking water systems. In most water utilities disinfection of the water represents an important barrier, but microbial barriers may also be achieved by other actions, for example in the catchment area.

Based on experiences from Norway, Sweden and Finland, this guideline is a helpful tool for implementing Water Safety Plans. The guideline explains the “barrier concept” and assist water utilities as well as their their consultants in determining what actions to take to ensure that the microbial barriers in their systems are sufficient – and that the water is safe to drink.