Plumbing a pond in the following manner can make a significant minimum maintenance and energy efficientcy difference in the over all life of the pond and its pump.
We strongly recommend always placing the pump in a "flooded suction" position. See this article on our site for more on the subject of “flooded pump positioning”.
Whether you are using an open air/submersible type or a centrifugal pump, it is to your minimum maintenance advantage to place the pump below the surface water level of the pond. Pumps do a better job and can last longer if they are provided with a flooded suction. Submersible /open air type pumps do not have the ability to lift water. Never place a submersible /open air type of pump above the surface water level of the pond.
We always place all pumps, even when we use submersible /open air types, outside the pond, below surface water level. We also place the pump in a vault. We use dry vaults for centrifugal pumps: dry vault/pumphouses. We use simple irrigation valve boxes for submersible/open air type pumps. Locate the pump close to the pond as possible, near the drain: drain links. Whether it is an open air or centrifugal pump, always place an isolation valve: valve links between your drain or other initial water intake system and the pump, then install a suitable leaf trap before the pump.
Pipe size and elevation is very important to obtaining energy efficiency and minimizing maintenance. Pipe size should not be based on pump port size but on rise, run, length/distance of pipe runs, and flow rate desired. Friction Loss Chart link.
We always build systems with as much of the plumbing below the surface water level of the pond as practical/possible, especially the suction side of the system. This provides the pump with the all important flooded suction. All pumps used in pond systems, “like” to “discharge” water, not lift and discharge. The greater the distance the pump is from the pond, the greater the importance of this issue.