Buying Guide: Water Garden Pumps

Water gardens require water movement to ensure recirculation and aeration, which are necessary to maintain a healthy environment. This can be accomplished by installing a pump or filter. 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. Pumps can also be used in water gardens to power fountains or other water garden items. Before purchasing a pump for your water garden, consider the following:

• Do you have a small or large pond?
• Will the pump be used for filtration or to power a fountain?
• What size pump will work best for your pond?
• Do you know how to calculate pond volume?
• Will you be introducing plants and/or fish?

Types and Size Calculation

Water garden pumps come in a variety of types and styles, including submersible, external, magnetic drive and direct drive. Each one offers certain advantages for specific applications. You'll want to evaluate your needs in relation to each type before you make a decision. For example, a pump used purely for water circulation differs from a pump required to power a stream or waterfall. Calculating the size pump needed is also an important factor and 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.

Submersible Pumps: Just like the name describes, submersible pumps are designed to be wholly submersed in water, in the deepest part of the pond. A big advantage to this type is that they are easy to install. Submersible pumps work well in environments that capitalize on a natural setting as there is no need to camouflage the pump. Submersible pumps also run very quietly so they are not distracting in your garden. 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.

• 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
• Submersible pumps range in size from 50 to 5,000 gallons per hour
• Submersible pumps can generate higher energy costs than other types
• For smaller ponds, submersible pumps are generally more economical

External Pumps: External pumps are reliable, affordable and energy efficient. They 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. Make sure you know whether the pump you choose is self-priming or able to draw its own water. Pumps that are not self-priming can burn out a motor if the power shuts off momentarily and then returns, so it's best to protect against this occurrence by installing a check valve.

• External pumps 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. Magnetic drive pumps are 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. This type of pump does 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, cost-effective operation
• 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. Direct-drive pumps achieve significant head height so they tend to work well for fountains or waterfalls. 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.

• Typically more expensive to operate
• Ideal pump type for fountains or other accessories
• Pushes water rather than pulling it
• Not easily repaired by the user

Pump Size Calculation: Gauging the correct size for your water garden pump will ensure your pond receives the proper water circulation. Unless the pump you buy is already configured with a built-in fountain head, you'll need to calculate how much a pump can handle before you choose a certain size or model. 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. In order to determine the size pump you'll need, you must calculate several key measurements.

Water Garden Pump 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.) Head height Horizontal distance / 10' + vertical height above water level = head height Pond volume Pond volume (gallons) = 7.5 x average width (ft.) x average length (ft.) x average depth (ft.)

Features

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 constructed of stainless steel and are more expensive. However, they offer greater energy efficiency and lasting operation.