The aim of this study was to investigate accumulated experience with water safety plans in one of the first countries to adopt systematic preventive management for drinking-water safety. Water utilities in Iceland have had a legal obligation since 1995 to implement a systematic preventive approach to secure safety of drinking water and protect public health. The water utilities responded by implementing either an adapted HACCP (Hazard Analysis Critical Control Points) model for larger water utilities or a simpler five step model for smaller water utilities. The research was carried out at 16 water utilities that serve about two-thirds of the population of Iceland. Both qualitative and quantitative methods were used with the aim of analysing if and what benefits water safety plans bring for water utilities and what is needed for successful implementation and operation of such systems. The results of the study show that numerous benefits and even the process of going through the implementing process were considered to be of advantage and change the attitude of the staff and the utility culture. Some obstacles and shortcomings came to light, such as lack of documentation and lack of regular internal and external audit. There was little communication with the public, although some mentioned that good public relations are important to succeed with water safety plans. Many important elements of success were revealed of which intensive training of staff and participation of staff in the whole process are deemed the most important. It is also important to have simple and well-structured guidelines, and good cooperation with the health authorities.