Centrifugal pumps transport liquids by using pressure. Because they are relatively uncompressible, the liquids are not condensed or pressurized; instead they are imparted with centrifugal force, the force that causes substances to move away from their center of rotation.
12 volt pumps are constructed out of aluminum, cast iron or stainless steel though some models have plastic housings. Because of the low amount of power these pumps use (less than one horsepower), the output is much lower than that of general purpose, industrial or commercial grade pumps. They are frequently small and compact enough to be portable and consequently are used for temporary jobs. 12 volt pumps are found on personal watercraft for water bailing purposes in case of emergency.
They are also used for camp or outdoor showers, watering gardens and pumping out a flooded basement. There are three main kinds of centrifugal pump usages: chemical, water and trash. Because of their size and energy, 12 volt pumps are generally not designed to pump the solids and debris usually found in waste water. Depending on the construction, however, some 12 volt pumps may be used to transfer small batches of liquid chemicals.
Centrifugal pumps are basic machines with few parts. The central component is an impeller which is very similar to a propeller except that the blades are not as sharp and they create suction instead of propulsion. The impeller is kept in a volute, or casing, and is mounted on a rotating shaft that connects to the motor.
As mechanical energy powers the shaft, the impeller turns as well, its vanes imparting kinetic energy to the fluid which follows the expanding volute to the discharge opening. Though the speed of the liquid is reduced, the pressure increases; 12 volt pumps can transport up to 10 gallons per minute. The maximum lift is about 30 feet with small or miniature pumps offering around 5 feet of lift. The pump diameter for a 12 volt centrifugal pump is often just a few inches.
Miniature 12 volt pumps are handheld and can be dropped into a well hole or river to lift water. Some models are submersible while others are able to run dry. Accessories are available to suit the demand and include removable strainers, hose barb connections and anti-clog measures. Many of these pumps need to be primed before they are used to expel air and allow water to be drawn in by the suction.