Abstract: An apparatus for permitting the periodic introduction of a fluid into a marine plumbing system for zebra mussel control and winterization purposes, comprising:a) a "T" shaped member having first second and third external apertures and a continuous interior passage which is communicatively connected to each aperture, the first and a second aperture further being permanently communicatively coextensive with flexible conduit members of the marine plumbing system;b) a valve, connected to a third aperture, for controlling the ingress of zebra mussel killing fluids and antifreeze fluids, through the third aperture, into the marine plumbing system, the valve having a first end connected to the third aperture of the branched member and a second end which is connectable to an external fluid source, the valve further having a closure member and a control arm connected to the closure member;c) a cap for connection to the valve second end; andd) clamps for connecting flexible conduit members of the marine plumbing system