Reduced velocity aerator stack systems (RVASS) are sanitary stack systems that use specialised fittings and pipework configurations in order to eliminate the need for additional venting required in traditional sanitary stack systems.

RVASS is a sanitary stack system that uses proprietary aerator junction fittings in stacks at each floor level where sanitary fixtures are connected. A de-aerator must be included at the base of the stack and at the base of offsets in RVASS stacks.