Currently common hot water temperatures above 60°C for Legionella prophylaxis cause high heat losses. With the filtration system C-MEM Eco-3D Legionella can be safely retained already at the house entrance of the drinking water supply. No more biofilm is formed and the entire piping system remains sustainably free of legionella. As a result, hot water temperatures can be lowered to approx. 45°C and valuable heat energy can be saved. The system was successfully implemented and tested in a demonstration project in Germany with 9 residential units. The energy savings were up to 33% compared to similar residential buildings without C-MEM Eco-3D. Regular microbiological testing also independently confirmed that the system was germ-free.