A shut-off valve assembly for regulating the flow of fluid through or from a fluid line. The assembly comprises: a body attachable to or within a fluid line and having a chamber therein with inlets and an outlet for fluid from the fluid line; a valve seat that provides the outlet; a baffle arrangement including a baffle housing; a valve member having a sealing member movable between a shielded position, whereby the sealing member is substantially shielded by the baffle housing from a fluid stream moving from the inlets to outlet, and an unshielded position, whereby the sealing member can be forced by the fluid stream against the valve seat to seal the outlet; and a solenoid-spring drive for moving the sealing member between the shielded and unshielded positions.