The three-way shut-off valve is constructed of solid gray PVC, has Buna-N seals, and a rotating flag handle. The valve can withstand a maximum operating pressure of 125 psi and a maximum temperature of 140 degrees F. The handle has 180-degrees rotation and lies directly over the open port. When the handle is rotated 90-degrees from either port, flow is shut off to both outlet ports. Since the bottom port on the valve is common, the valve can be used as a diverter or a selecting valve. These valves can be used to conveniently hook three instruments together, as well as testing various gages and transmitters.