How Does a Garden Pond Pump Work?

A garden pond.

A garden pond pump is a remarkably simple machine with only a single moving part. Here is what you need to know about your garden pond pump.


The most reliable and efficient pond pumps are submersible with all electrical parts well isolated from the water. The three principal parts of the pump are the impellor that spins and drives the water, the water intake pipe that is also attached to filters to clean the water before it enters the pump and the outlet pipe which delivers the cleaned water back into the pool. If the outlet pipe drives the water above the surface, the water will also be aerated or oxygenated. This is important if there are fish in the pond.

Simple Mechanics

The main body of the pump houses an electric coil. Suspended on a stainless steel shaft at the center of this coil within a water pipe is a cylindrical magnet that forms the core of the impellor. The impellor is fitted with vanes that run very close to the inside of the pipe. When the coil is live the field that is created by the coil, causes the magnet to spin around the shaft. The impellor veins attached to the magnet force the water through the tube and the centrifugal force working on the water forces it to leave the pump at 90 degrees to the pipe. The speed of the impellor controls the speed of the water flow. Because the spinning of the impellor is induced by the field created by the live coil there are no gears to worry about and the risk of a break down is almost eliminated.


As the water is drawn into the pump through the inlet pipe it goes through three filters. The first filter is a coarse mesh that catches large objects in the water. The second filter is a much finer filter that can catch soil and sand particles and small insects. The third filter is usually made of foam and catches anything that is big enough to jam the impellor and most algae. As these filters become filled, the flow of water will be reduced and indicate that they need cleaning. The filters can usually just be slid off the end of the inlet pipe to be cleaned but the pump should be switched off before the filters are removed. Cleaning the filters is usually just a case of flushing them through with water in the opposite direction to normal.

Aeration or Oxygenation

A backyard pond.

Water garden pond pumps are also used to oxygenate the water, especially if there are fish in it. This is achieved by simply driving the water from the outlet pipe above the surface level of the pond and allowing it to fall back into the pond. The two most popular methods are a fountain or a waterfall.

General Maintenance

Pond pumps, apart from filter cleaning, are totally maintenance-free. The only problem that has to be prevented is a fall in the water level so that the pump is exposed and no longer cooled and lubricated by the pond water. The level of the water should always be maintained so the pump is submerged. A water supply pipe with a float valve is the ideal solution to this possible problem.

A pond pump will maintain the health of your pond and any occupants for many years requiring no more attention than occasional filter cleaning.