What Kind of Pumps Are Available

Pond pumps come in many shapes and sizes. Although they all do basically the same thing (pump water) they differ in the way they go about the job and how they actually work. With a little basic understanding you will have a better idea of which one will suit your specific needs. Some pumps are designed to work only submerged in water while others are designed to work exclusively out of the pond (external) while still others can be used in either application.
The first pumps available were out of pond (external) pumps and submersible sump pumps. These were direct drive pumps because the impeller was directly connected to the electric motor via a shaft. They are cooled by the water and the impellers are somewhat heavy so the motor needs to be strong enough to sufficiently rotate the impeller. The motors were wound with copper and protected by seals that kept the water away from the pump motor. They produce large volumes of water and are still used in applications where high head heights are required. Because of there design, they are not generally energy efficient.
Many years later the first magnetic pumps became available. These pumps featured lighter impellers and no seals and the small motor spins a magnet via magnetic induction and is fully encapsulated in epoxy to prevent damage. The result is a more compact design and much more energy efficient. They can also be used either submerged or out of pond. They do not produce the high head height of a direct drive pump. When the pump is energized, the magnet spins the impeller but you never know for sure what direction it will spin so the impeller is designed to work in either direction. Newer Hybrid pumps are able to operate the magnet to spin the impeller in one direction which has benefited in more efficient impellers which can produce additional volume and higher head heights. These Hybrids are known as Asynchronous pumps. These newer designed pumps are gaining favor as they are available in larger sizes, even above 6000 gph. Like a mag pump, they can generally be used submerged or out of the pond. The only caveat is that the high efficiency requires very close tolerances inside the pump which can make them susceptible to scale buildup and clogging in hard water locations. They need to have good prefilters to keep out debris, and regular cleaning to remove any lime scale or other water deposits.