Thread from the WWn Wiki - originally developed by iSoaker, Andrew, and Martianshark
1 Principles of operation
1.1 Piston Pressure
1.2 Air Pressure
1.3 Elastic Bladder Pressure
1.4 Spring Pressure
2 Principles of construction
3 External Links
 Principles of operation
Homemade water blasters can function in a variety of different ways. A device as simple as a bucket of water can be considered a "homemade water blaster", but it is common to use this term to refers to devices that utilize a more complex system, particularly such systems that can project a stream of water.
 Piston Pressure
There are two main setups to direct piston blasting: One that uses check valves and draws from a water source separate from the nozzle, and one that doesn't. The latter is a very simple syringe, where the nozzle is dipped in the water source and the pump pulled back to load, then the pump pushed to shoot. (The Waterzooka is a common example of this.) The former uses check valves and draws water from a source separate from the nozzle.
 Air Pressure
Air pressure is a very broad category covering a wide variety of possible designs. In a conventional Air Pressure Homemade (APH), the user pumps air and water from a reservoir source into separate chambers where the air is compressed. The design is similar to many XP Super Soakers and a few 2011 Water Warriors blasters. The APH label usually refers to this kind of design but can refer to any water blaster that primarily relies on air pressure.
Other common air pressure homemades designs include the Pressurized Reservoir Homemade (PRH), the Low Pressure Dropoff (LPD) design, Constant Air Pressure (CAP), and the water cannon, which all have overlapping features some way or another. The PRH is perhaps the simplest homemade water blaster design to start with, but is not as easy to make them useful for water warfare. The LPD simply uses a high air to water ratio for low pressure dropoff, and the CAP uses a high pressure air source (i.e. HPA tanks often used in Paintball) and a regulator to maintain nearly perfectly constant pressure. The water cannon is designed to rely on conventional pressurization methods but exhibit very high power levels close to that of a firehose.
The air and water may be separated by a piston or not, depending on the design. CAP's, LPD's, and water cannons typically separate it.
 Elastic Bladder Pressure
The Constant Pressure Homemade (CPH) is the conventional elastic powered homemade, where the user will pressurize water within a flexible, elastic bladder. The use of an elastic bladder allows these homemades to be fired from any angle and does not require pre-pumping. Latex rubber is virtually the only bladder material ever used, and for homemades, such a bladder can be created with bike tubes, latex rubber tubing (LRT), and latex party balloons. Stacking layers of these items is almost always necessary to achieve higher end performance.
Rubber bladders achieve relatively constant pressure as well as some air pressure systems with a high air to water ratio. However, CPS and constant pressure typically refers to bladder-based pressurization.
 Spring Pressure
Spring powered homemades use a piston and spring as a pressure chamber. The pressure chamber layout bears similarities to some air pressure designs in that there is a piston to seal a cylinder and keep the water out of the spring. Spring powered pressure chambers face many major limitations, such as volume, pressure, and strength required, that make them an unpopular option so far, and to date, no spring powered homemade has yet been built.
 Principles of construction
The most common building material for homemade water guns is plastic piping. There are many types of plastic piping available, but the dominant type is poly vinyl chloride (PVC). PVC is safe for water, lightweight, inexpensive, and readily available at many hardware stores. The primary limitation of PVC is high-pressure. If an air compressor is being used to charge the homemade with pressurized air, it is recommended to use metal piping as a safer alternative to plastic.
Super Soaker Central Homemades - http://www.sscentral.org/homemade/
Aqua Labs Water Balloon Launcher - http://aqualabs.tripod.com/thelaunchers.html