Filter on the return for flange assembly with immersed attacks the Fri Filters are filters on the return designed for flange assembly directly on the tank cover, with immersed bsp threaded connections. The inspection lid allows easy replacement of the cartridge and rapid cleaning of the housing. The filtering element is made with high efficiency materials, guaranteeing a large accumulation capacity of the contaminant to protect the system. The Fri Filters are equipped as standard with integrated bypass valve, while the clogging indicator, both visual and electrical, is to be ordered separately.