- 2-inch-by-24-inch Schedule 40 PVC pipe
- 1¼-inch-by-24-inch PVC pipe
- Two 2-inch PVC caps
- Two 1¼-inch PVC caps
- 1¼-inch PVC coupler
- Buna-N 1.6-inch ID by 0.21-inch CS O-ring
- PVC glue (8 ounces is plenty)
- Tube of waterproof silicone grease
Summertime means rising temperatures—and, often, rising tempers. If your friends and family want to beat the heat without beating each other, there’s a surefire option: squirt-gun fight! But shelling out for a few $20-or-more water weapons can rapidly thin a wallet. That’s why you should take matters into your own hands, visit the hardware store, and exercise some garage ingenuity to build an inexpensive yet durable arsenal of Waterzookas. Popular Science likes this version from the website Instructables.com, but we tweaked it to stay current with the latest water-gun technology. Follow these instructions to keep your cool.
Homemade Water Blaster
Cut: Take the thinner 24-inch pipe , and saw off a 2-inch-long piece. Smooth the edges with sandpaper.
Drill: This is the fun part. New water guns let you pick nozzles that can soak people in a variety of ways. Imitate them by drilling one ¼-inch-diameter hole, or several ⅛-inch-diameter holes, in the end of one 2-inch PVC cap . A small, ⅛-inch-wide slit also works well. (Our favorite configuration? Three holes that deliver a shotgun-style blast.) Cut or drill a larger, 1¾-inch hole in the other 2-inch cap; this will be your piston guide.
Glue: Assemble the piston by applying PVC glue  to one end of the 2-inch pipe you sawed off in step A and to one end of its 22-inch counterpart. Insert both glued ends into either end of the PVC coupler . Ease the O-ring  over the 2-inch piece of pipe, then glue one of the 1¼-inch caps  to the 2-inch piece.
Grease: To build the gun’s body, glue the nozzle (the 2-inch cap with the small hole(s) you drilled) onto the 2-inch-by-24-inch PVC pipe . Let the glue dry for 15 minutes, then dab some grease  inside the pipe.
Assemble: Stick the piston into the body, then push, pull, and wiggle it around to evenly distribute the grease. This will create a smooth, watertight seal. Next, work the piston guide (the 2-inch cap with the 1¾-inch hole you made) over the piston, and slide the piston guide onto the body. Don’t glue it! Take the other 1¼-inch cap and glue it to the piston.
Douse: Your Waterzooka is ready for action. Dip the business end into water—a lake, a pool, a bucket—pull the handle to suck water into the barrel, and then push it in to fire. Just make sure to build a few for your spouse, kids, and mother-in-law so they can defend themselves. Well, maybe not your mother-in-law.
Time: 2 hours
Cost: About $15 for a bunch of guns
WARNING: Kids, you need adult supervision. Launch only outside while wearing eye protection, and mind your aim (matches were designed to start fires).
This article originally appeared in the July 2013 issue of Popular Science. See the rest of the magazine here.