Loosen the thumbscrew on top of the valve. Move the handle so that it lines up with the middle port, with one port on each side. Remove the eight screws that hold the top section to the valve body with a Phillips head screwdriver.
Grasp the valve handle and work the valve mechanism out of the valve body. Spread PVC primer around the outer edges of the pipe and the insides of the valve ports. Allow the primer to dry for one minute.
Spread a layer of glue around the edges of the first pipe you will connect. Push the pipe into the valve body firmly and make sure it goes all the way in. Repeat the gluing process to connect the remaining two pipes to the valve body. Note that when you install the pipes, make sure that the pipe connected to the side labeled "Inlet" goes to the pool pump.
Allow the glue to set for 24 hours. Place the valve mechanism back into the valve body. Reinstall the eight screws to secure the top to the valve body with the Phillips screwdriver. Tighten the thumbscrew to lock the valve into the desired position.