A valve comprising: a valve body； and a valve stem disposed at least partially within the valve body, the valve stem comprising a sidewall defining a central lumen and at least one opening in the sidewall, wherein the valve is adapted to prevent fluid flow through the lumen when the at least one opening is disposed within the valve body and permit fluid flow through the lumen when the at least one opening is exposed from the valve body, and wherein the valve is essentially free of a spring.
