Things You'll Need
Instructions
Cut the 3/4-inch PVC to a 15-inch length. Cut the dowel rod to an 18-inch length. Sand down the dowel until it fits inside the PVC pipe. Glue a 3/4-inch plastic end cap on one end of the PVC pipe. Allow the glue to dry and drill a hole about an 1/8 of an inch in the center of the cap.
Epoxy glue the rubber 3/4-inch O-rings to each end of the dowel rod and allow it to dry. Drill a 1/2-hole in one end of the dowel about an inch from the end. Glue a 1/2-inch piece of dowel about 6 inches long into the hole to be a handle. Allow the glue to dry.
Insert the end without the handle into the PVC pipe. Pull it back and forth and observe how it works as a plunger as the pressure creates tension. Push the plunger all the way in. Put the end with the end cap into a bucket of water and pull. Remove the water gun and push the plunger in, causing the water to shoot out.