A valve assembly includes mutually opposed first and second valves, each having a casing that defines a respective through passage. The through passages include internally circumferential valve seats at contiguous ends thereof, against which respective movable valve members are biased. The respective valve members of the first and second valves engage one another when the first and second valves are brought together to urge the valve members away from their respective seats to open the first and second valves. A coupling member holds the first and second valves together, and a travel limiting element restricts the travel of at least one of the valve members in the direction away from its valve seat to prevent the other valve member from engaging its valve seat when the first and second valves are together, thus preventing the other valve from closing due to the flow of fluid through the valve assembly.