Features such as waterfalls, streams and fountains add a whole new dimension to a garden pond. All of these features require a pond pump to function correctly. The garden pond pump should only be powered by an outdoor outlet unless it is a solar-powered pond pump. This outlet must have a Ground Fault Interrupter (GFI) installed on it. These devices serve to break the circuit when water comes into contact with any electrical object. Without such a device, safety cannot be guaranteed (water and electricity are never a good combination!).
The outdoor outlet needs to be a good distance from the pond. A minimum distance of 6 feet is acceptable, although a distance of 10 feet is better. This ensures that the outlet does not come into contact with the water when you are working on the pond pumps or filters.
Pond pumps are rated according to how much water they can move over a given time. They carry a rating listed as GPH (flow rate), which stands for Gallons Per Hour. This rating refers to the amount of water that the pump can move in one hour over a height of one foot. Therefore, if your garden pond pump will be carrying the water more than a foot in elevation, this must be taken into consideration when buying a pump.
Solar pond pumps are not very powerful and generally solar is only used to power a pond fountain pump.
Some pond pumps are positioned above the water and some submerged. Each has its own particular advantages and disadvantages.
Above water pumps are very easy to maintain. They are also kept clear of many of the pollutants such as sand and gravel that may have a negative impact on the performance of submersible pumps. These garden pond pumps, however, can be very pricey and the more powerful units may generate a lot of noise thereby detracting from the calming effect of the water features they power. Submersible pumps are more popular for small ponds. These pond pumps are placed directly into the water where they operate almost silently. Of course, if there are problems with these pumps they have to be pulled out of the water to be repaired.
How to calculate which size pond pump for your pond
The amount of work required by a pond pump depends both on the height and the distance the water must be carried. For every 10 feet of horizontal distance the water must be moved, you need to factor in a height of 1 foot. Total height is determined by measuring from the top of the pond pump to the top of the waterfall or fountain. For example, a waterfall one foot above the ground and pump located at the bottom of a three-foot deep pond, the water must be raised four feet to fill the waterfall. Where the size of the waterfall or stream is concerned, every inch of width is the equivalent of 150 gallons over the course of an hour. A waterfall with a 4-inch spillway will require a pond pump that produces 600 gallons per hour (3000 litres/hour).
The pond pump should circulate the water at least once per hour. To determine the volume of your pond, multiply the length x width x depth. For every square foot of volume there are 7.5 gallons of water. So, a pond that has a volume of 50 cubic feet will contain roughly 375 gallons of water. From this figure, you can determine the GPH of flow rating needed for proper circulation of the water.