Instead of buying a water gun in stores, you can build your own gun using inexpensive parts bought at a hardware store and an empty plastic bottle. Homemade water guns can be modified to store more or less water for quick firing, light-weight guns or bulky guns that can fire multiple shots between refills. The gun works by forcing water up through a plastic tube and out the front end with enough force to send the stream at your target. A homemade water gun does not require power tools or other hardware, meaning it can be assembled by kids as well as adults.
Empty a 20-ounce plastic bottle. Remove the wrapper from the bottle. Remove the cap and place it on a hard, flat surface.
Push down on the center of the bottle cap with a Phillips screwdriver until you poke a hole through the cap. Tighten the cap back onto the bottle.
Thread one end of 1/4-inch-wide, 2.5-foot PVC tubing through the hole in the bottle cap and down to the bottom of the bottle. Expand the hole with your screwdriver if it does not fit.
Apply duct tape around the top of the hole to cover any gaps between the tubing and bottle cap. Do not attach the cap to the bottle with tape as you need to be able to remove the cap to fill the bottle with water.
Insert one end of a 1-foot-long by 1-inch-wide piece of PVC pipe into a 1-inch-wide PVC elbow joint. Insert a 6-inch-long piece of 1-inch-wide PVC pipe into the other end of the joint. The L-shape will resemble a gun.
Snake the free end of the PVC tubing up from the short end of the gun and through the long end so about ¼ of an inch of the piping protrudes from the long end of the gun. You will have a bit of open tubing between the bottom of the gun and the bottle.
Secure the tubing at each end of the gun with 1-inch pieces of duct tape. This will hold the tubing in place when you use the gun.
Grip the bottle cap and twist the bottle counterclockwise to remove it from the gun leaving the cap still on the tubing.
Fill the bottle to the top with water. Twist the bottle clockwise back onto the cap.
Hold the gun in your off hand and the bottle in your strong hand. Aim the gun and squeeze the bottle as hard as you can to send water through the tubing and out the front of the squirt gun.
Refill the bottle when it gets low on water.
PVC tubing, pipes and joints can all be bought at a hardware store.
Use larger plastic bottles such as a one or two-liter bottle to increase the time between refills.