A system separation device with at least one pressure-proof tank for containing a liquid that forms a predetermined liquid level in the tank, above which level there is a gas cushion. The device contains an inlet in the upper region of the tank for fluidly feeding the tank from a first fluid system, and an outlet in the lower region of the tank for forwarding the liquid to a second fluid system. To prevent the germ-infestation of the inlet, at least one germicide material is arranged in the region of a gas cushion above the liquid level.