A system (10) includes a water and/or air inlet (20), connectable to a water supply pipe (5) for a sanitary apparatus (1). An outlet (40) connects to a sewage outlet pipe (4) downstream of the sanitary apparatus. The inlet leads from a suction box (30), which starts the outlet (40). A motorized ventilation device (31) conveys air from the inlet (20) to the outlet (40). A siphon (32) is at least partially filled with water (33) from the water supply device (6). The ventilation device (31) and the siphon (32) are mutually in series between the inlet (20) and the outlet (40). The suction box (30) includes a further siphon (321), connected between the supply pipe (5) and the outlet pipe (4) and is arranged in parallel with respect to the siphon (32) and the device (31). The further siphon (321) is at least partially filled with water.