The Super Soakers revolutionised water warfare, by using air pressure (and in CPS weapons rubber chambers) to propel water.
The first super soaker, then known as the Power Drencher was released in 1988 and was designed by Lonnie Johnson. Larami marketed his invention and continued innovating in the water pistol field.
Early models were fairly simple. The pump forces air into the water tank. A tube allows water to leave the tank under the action of air pressure when one pulls the trigger. The advantage of this design is that it is simple. It however has several disadvantages :
Pressure drops rapidly when you start firing: you get very little shooting time at full power/range.
You are pressurising your whole water tank: If you have a 1 litre tank, 1/4 full you need to do a lot more pumping than when the tank is 3/4 full in order to get the same pressure.
You lose all pressure when you refill. This makes in combat refills dangerous as you will be defenseless during the refill.
Peak flow rates for this series of weapons tends to be in between 10 and 60 mL/s, depending on nozzle size. Some small pistol size weapons still use this system.
Later models used a slightly different system. Instead of just forcing air into the main tank, the pump drew a mixture of air and water into a separate firing chamber. Only this chamber was pressurised. This improvement reduces pumping considerably, especially when you are low on water. It also means you can refill while still being able to shoot (although obviously only as much as you firing chamber holds).
Full sized members of the XP series of weapons still use this system. They typically have flow rates in between 60 and 90 mL/s.
The most advanced super soakers use what is known as the CPS system. Since air pressure alone is not capable of propelling large quantities of water sufficiently far, in weapons such as the CPS 2000 the firing chamber is made of rubber.The rubber stretches when the firing chamber is filled with water and air, adding to the air pressure to give more power. The only problem with this system is that it is very easy to get through vast amounts of water, especially if you are a bit trigger-happy. These are the most powerful super soakers available. My CPS 2000 has a peak flow rate of 850 mL/s! Most weapons in this family have flow rates in between 100 and 500 mL/s, depending on the nozzle selected.
Many of the more recent models have have several nozzles to choose from, depending on whether you want to save water or totally drench someone. Larami have also experimented with multiple barrels, most recently with the Monster XL, a twin barrel monster that even has a bipod. Some super soakers have back packs to enable you to carry large amounts of water.
Although a number of other companies manufacture water guns the Super Soakers tend to have the upper hand especially with the more powerful weapons.
stats and some facts pulled from www.isoaker.com