Abstract: A housing is divided into two chambers. A tube connects the two chambers. The end of the tube forms a valve seat on each end. The valve seat in one chamber angles upward and the valve seat in the opposite chamber angles downward. A flapper valve is attached above the top of the valve seat which angles upward, and at the bottom of the valve seat which angles downward. Gravity acting upon the flapper valves will hold one in the open position and the other in the closed position unless it is opened by a flow of fluid. Turning the housing upside down will reverse the position of the flapper valves so that the permitted fluid flow will be reversed.