The water supply must be safe and sustainable. This requires a regulatory compliance, selection of an optimal water treatment process, timely response to water quality incidents as well as maintaining internal skills and knowledge among utility personnel to keep appropriate operational standards in the long run. Water supply services in Japan face various challenges, including a shrinking revenue base due to a declining population as well as a mass retirement of the baby-boomer generation. The Japan Water Research Center conducted questionnaire surveys and based on our findings developed the ‘knowledge transfer support system for water treatment technology’ for utilities to maintain internal skills and knowledge in the face of shrinking labour forces in the water sector. The system consists of three components: the database on water treatment technology, learning program on water treatment technology, and the assessment tool for knowledge transfer on water treatment technology.