Water wars are a refreshing way for kids to stay active and cool on a hot summer afternoon. Forget about the squirt guns of days past. The new "weapon" of choice for water wars is a water cannon--provided the water pressure isn't too high. You can make your own water cannon with PVC pipe or try making a few and getting the neighborhood kids together for hours of good, wholesome summertime fun.
Cut your 1 ½-inch PVC pipe to 2 feet in length with the hacksaw. Trim and sand the edges smooth. Drill a ½-inch hole in the middle of the end cap, starting small so you can determine how far you want the water to shoot. If a larger opening is desired, drill a larger hole.
Glue the end cap to one end of the PVC pipe with pipe glue. Allow to dry for 20 minutes.
Insert the wood dowel into a 3-inch length of 1-inch PVC pipe and apply glue. Allow to dry for 20 minutes.
Make your plunger by rolling the O-ring over the 1-inch PVC pipe containing the dowel. This will keep water from leaking around the pipe.
Push the plunger you made in Step 4 all the way into the open end of the larger pipe--O-ring end first, which will minimize water leakage. The O-ring will create a rubber gasket between the two pieces of the water cannon.
Submerge the end cap of your water cannon in water and pull back on the wood dowel to fill the tube. Aim your water cannon and push the dowel in as hard as possible.