Homemade Pump-Style Water Gun

After making a simple water gun that required no valves and had limited function, I wanted to make a continuous-pump water gun that would work more like a Super-Soaker. I tried various materials for valves and various methods of placing the valves in the gun, and finally came up with this solution.
You can look at a larger version of the composition of this hand-pump water gun by clicking on the sketch below. Print and take it with you when shopping for materials. Below is a video showing how to put together the valve system and the piston for the pumping action. You can buy check valves at a hardware store, but they are too bulky for a kid’s water gun. Besides, I wanted to make this project something that could be taught in a grade school science class for children to make and understand the mechanics of water pumps.
Materials for Water Pump Gun:
1″ and 3/4″ PVC
1″ PVC Tee
1″ to 3/4″ bushing
1″ to 1/2″ threaded reducer
1/2″ to 1/4″ nylon barb
1″ rubber washer
3/4″ metal washer
Inner tube rubber
Piece of thick, firm foam (like from a flip-flop)
Epoxy glue
End cap for piston arm (either 3/4″ or 1/2″)