This thesis contains the product development work towards a, for Alfa Laval Lund AB, alternative product to eradicate Legionella bacteria from domestic hot water systems. The existing product at Alfa Laval Lund AB, the AquaProtect, is having problems to reach costumers with small and medium size systems. The product developed in this thesis should be in a much more attractive price range for small and medium size systems. It should also work in any domestic heating system with circulation. Making it possible for, for example, the vulnerable people at elderly care housings to have Legionella bacteria free water.