Water Garden Pumps
Pumps keep the water in your pond healthy by evenly distributing nutrients in the water to fish, plants and other aquatic life. Running water also prevents stagnation, cuts down on algae and mosquitoes, and ensures that oxygen levels are distributed throughout the pond.
This guide will show you the differences between different pump types, and how to choose one that's powerful enough for your water feature.
Water garden pumps come in a variety of types and styles, including submersible, external, magnetic drive and direct drive. Each one offers its own advantages.
Submersible Pumps: Designed to be wholly submersed in water, in the deepest part of the pond.
- Easy to install
- Work well in environments that capitalize on a natural setting
- No need to camouflage the pump
- Run very quietly so they are not distracting in your garden
- Submersible pumps can be used to drain your pond, if needed
- Place pumps either directly into your pond or in a skimmer box or pond vault
- Range in size from 50 to 5,000 gallons per hour
- Can generate higher energy costs than other types
- For smaller ponds, submersible pumps are generally more economical
Tip: With submersible pumps that use oil in their operation, there is the danger of the pump seal breaking and leaking harmful oil coolant into the water, which can hurt fish. If you have fish or other aquatic life in your pond, you'll want to look for a submersible model that does not use oil.
External Pumps: External pumps can move a high volume of water and still manage to outperform submersible pumps in energy costs. Although not as quiet as submersible pumps and a lot more complicated to install, external pumps are generally more reliable.
- Available as self-priming pumps able to draw their own water
- Pumps that are not self-priming can burn out a motor if the power shuts off momentarily and then returns, so protect against this by installing a check valve
- Can be loud, disturbing the quiet of your garden
- Work well for larger ponds -- 1,000 gallons and above
- Offer long-lasting performance and easy repair
- Install external pumps in a dry location near your pond
- Require less routine maintenance than submersible pumps
Magnetic Drive: In a magnetic-drive pump, an electrical charge creates a magnetic field that causes the magnet on the impeller to rotate and pump water.
- Completely sealed and do not require lubrication
- Because they do not contain oil, magnetic drive pumps are safer for ponds with fish as oil leaks do not occur
- Do not generate high head heights, meaning it is unable to lift pond water vertically, which you might need to supply water to a fountain
- Work best in cleaner environments with little or no debris
- Highly efficient and cost-effective
- Since they have no seals to wear out, they require little maintenance
- Occasionally clean the impeller and its chamber to ensure efficient operation
Direct Drive: Direct-drive pumps have an enclosed motor that is powered by electricity, which turns the impeller shaft.
- Achieve significant head height so they tend to work well for fountains or waterfalls
- Typically more expensive to operate
- Ideal pump type for fountains or other accessories
- Pushes water rather than pulling it
- Not easily repaired
Tip: Some models seal the motor in an oil-filled shell with seals around the cord and impeller shaft. These are risky to use if you have a pond stocked with fish as there is an ever-present danger of water contamination if a leak occurs. Many newer pumps, however, feature alternative lubrication over oil that is safe for fish. Look for oil-free models if you house fish or other aquatic life in your water garden.
Calculating the size pump needed depends upon the size of your pond and also whether you are using the pump for filtration, water features or recirculation of water. The number of fish and plants your pond contains will also influence your decision, as larger fish populations have greater air requirements.
A good rule of thumb is that pumps should be able to pump out about half the pond volume every hour. So a pump that moves 500 gallons per hour would be appropriate for a 1,000 gallon pond.
To determine the size pump you'll need, make a few measurements and calculations.
Flow rate for filtration
- Filtration flow rate in gallons per hour (gph) = 0.5 x pond volume (gallons)
Flow rate for fountains
- For every inch of stream width at the top of the fountain, you need 100 gph at the height you're pumping
Flow rate for waterfalls
- Light flow = 50 gph x waterfall width (in.)
- Average flow = 100 gph x waterfall width (in.)
- Strong flow = 200 gph x waterfalls width (in.)
- Horizontal distance / 10' + vertical height above water level = head height
- Pond volume (gallons) = 7.5 x average width (ft.) x average length (ft.) x average depth (ft.)
In-line, utility, solids and axial pumps are just a few of the many varieties of water garden pumps that can be used to meet your exact landscaping needs.
- In-line Pumps: These pumps draw water through an inlet that connects to a hose so you can pull water from a remote location. All external pumps are in-line pumps.
- Utility Pumps: Utility pumps draw water through openings that screen out debris. When placing one into a pond, use a pump sock or other enclosure to reduce the amount of cleaning needed. If you use a pump sock, be aware that sock-like screening can cause a dry pump situation.
- Solids Pumps: These pumps draw water through a large opening and pump small debris through without clogging. For this reason, they can be placed into a pond without prefilters. Note, however, that this type is not safe for ponds with fish, frogs or other aquatic animals.
- Axial Pumps: These special utility pumps are designed for high-flow, low-pressure pond environments. Because they are large, they require piping that is large in diameter.
- Solar Pumps: Solar-powered pumps perform well in climates with a great deal of sunshine and save money by not requiring an outdoor electrical outlet. Solar pumps also work well if your fountain is located a distance from the power supply. However, flow rate is minimal compared to typical voltage.
- Heavy-Duty Pumps: Heavy-duty pumps are typically made of stainless steel and are more expensive. However, they offer greater energy efficiency and last longer.