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/Aquatic Gardens, Design, Construction & Maintenance

Pumps: An Introduction

By Bob Fenner

 Nice to have an alternate discharge to hook up for cleaning

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

V. 1 Print and eBook on Amazon
V. 2 Print and eBook on Amazon

by Robert (Bob) Fenner

There are many different types of water-moving pumps and motors used for water features. You must plan for, select and install/engineer the right pump for your particular application: The pump type, size and orientation must be matched with the water-effects' size, configuration, plumbing/filtration/circulation systems to produce your desired results at a minimum cost.

Who owns your public utility? You do! Re-read the above paragraph; the savings from emphasizing the need for diligent pump research are the best money I can help you with.

Costs: Initial & Ongoing

Often, in the long run, the single largest expense of water effects is the electrical cost of running the pump(s) for water purification, filtration, aeration, circulation and ornament. A frequent approach to reducing operating costs is to shorten pumping operation time. In general, this is a very poor idea, especially in biological systems. In "living" systems, water effects with live plants, and/or fishes the pumps should/must run generally 24 hours a day.

Actual operating costs for running a pump, including purchase, service factor, application and energy can be determined with your manufacturer/distributor representative or a

pump engineer. Alternatively, the largest expense-factor, electrical cost may be easily calculated using the formula of multiplying volts times amps consumption and dividing out by your cost per kilowatt. If you need help, do call on your local utility and they will gladly help you.


How much pump is enough? As usual, it depends; principally on what effect is desired aesthetically & functionally. There are systems that are designed and built to have no to very little pumping. Then there are features that by virtue of poor, inadequate lay-out, depth, over-feeding, inappropriate size filters, and/or improper maintenance cannot be pumped enough.

When specifying a pump it is necessary to determine the water pressure (Head) and flow-rate (gallons per minute, hour) that the pump must supply.


If you're involved with an effect that has an appropriate filter system, plumbing, not too much food & fertilizer, and do not want it to be "out of balance" chemically or biologically, you are ready to ask the question: What is it I want from this feature that pumping will get me? What sights & sounds? What degree of clarity, cleanliness?

You do not need an advanced degree in fluid hydraulics to get beyond this point! By following the information in the Sections on plumbing and electrical topics, you should be able to assess the correct pump.

Most water features of a few hundred to a couple of thousands of gallons will perform functionally by circulating the water through the whole system about once per hour. Another rule of thumb is to select a pump and motor that will give you one gallon of flow per minute per foot surface area of the effect. Where in doubt, seek experienced help, or go to the next size up in flow-rate. For consideration of the factors of matching of filters to pumps and flow rate, please see the various and several Sections in this book on Filtration.

I purposely underlined functionally in the paragraph above.

Aesthetically the "end-user" may desire more or less apparent flow. If less, due to overwhelmed falls, errant jets, filters et al., circulated water should be diverted back to the water feature below water, with less fanfare. If you want more circulation, this should present no problems as long as the configuration of your water effect and the mechanical parts can accommodate it.

Selecting A Pump:

Should be done with the help of people who know the product and it's applications. Bring a drawing of the system basin/s, plumbing, filtration and topography & ask for advice, given what sights and sounds you want to produce. The equipment distributor will match your needs to a power or system curve for the available pumps and give you the skinny on installation, initial and ongoing costs.

A note: selecting pumps by horse-power alone can be extremely mis-leading! Ask your dealer to show you how to interpret which pump/motor combination is right for your system.

There are ways you can educate yourself to be able to figure the relationships between head pressures, resistances due to fluid, piping and filters; see the references at the end of this piece.

Pump Types:

Emerged, Out of the Water:

For most medium-size water effects centrifugal "swimming-pool-type" pumps are used. Many other pumps of less revolutions per minute, more/less flow-rate/pressure, specialized volute/applications are available and definitely worth looking into for the long-run.

Swimming-pool pumps often use more electricity, but have the power to generate the head-pressure and flow-rate you may want them to, especially to back-wash filters. Due to a wide range of efficiencies, appropriate application, up-front and continuing costs it is of primary importance to use the "right" pump.

Make sure and look into the possibility of two-speed (much less cost of operation at lower, regular setting), and higher "rated" pump motors. Don't miss out on the opportunity of saving real money by getting the best pump/motor combination available for your application.

About being outdoors. It's no fun to replace pumps entirely let alone bearings regularly from exposure to the elements. Do provide at least a simple housing/cover for your pump. Here's an artificial rock that is water proof, strong and lightweight that can act as a ready cover. Color and texture can be matched to other landscape elements. 

Submersible Pumps:

Except for the smallest, non-life-containing water features, submersible pumps are to be avoided. The reasons for this are several and significant:

1) They cost more to purchase and run per unit flow/pressure, counting electricity, flow, life-time, and up-keep labor.

2) Their wiring may be damaged, resulting in electrical shock or electrocution to humans or livestock.

3) The submersible motor may leak oil into the system.

4) The pump bodies rust/rot (oxidation/reduction) with time and water chemical treatment. This will stain the water feature and change the water chemistry.

All this being said/written, there is a wide range of quality of submersible pumps available. Some lines are far worse/better than others. Some features to look for if you're going to use a submersible:

1) Get one made for continuous duty, not an intermittent-use sump pump.

2) Select a pump with a stainless or brass body and a non-corrosive volute, the part of the pump housing the impeller. Second best are sturdy plastic housings. Avoid pot-metal and painted pot-metal pump bodies.

3) Get a pump with an adequate size mesh and surface-area intake screen.

4) Use a submergible pump with a thermal switch and if possible, low water off-switch.

Cal-vert Engineering (Cal-pumps) is premier in this field in my opinion. They are moderately priced, customer-service oriented, stand by their product and are (gasp) American made!

Some people like submersibles due to less initial costs for pump, plumbing and set-up. when you consider their negative sides and potential disaster.....To say it again: if at all possible, use an emerged or dry pump. They cost less to run and maintain per unit than one's that are made to go underwater; so much less that the difference in initial savings is lost in a few short months. Nuff' said?

Water and Electricity:

Do not mix! Follow the National Electric Code and local laws in wiring your pump. Use a Ground Fault Interrupter (G.F.I.) and provide a service switch.

Pumps & Plumbing:

We will dedicate separate pieces to discussions of plumbing and related matters. Here, I would like to emphasize some important facts relating plumbing and pumps.

Oversize your pipe! There are situations where plumbing can be too large on discharge sides, but these are rare in practice. The fitting size or bushing provided by the manufacturer should be your guide to appropriate diameter; do not reduce this size!

On intake sides of pumps, the plumbing should be bushed up (increased in diameter) in size. The least restriction should be presented. Remember; your pump is designed to push, not pull. Therefore, do not use intake filters (even though these are sold in the trade); but do use an appropriate intake-screen system or trap to keep trash out of the pump. Check and clean the intake of debris often.

Pump Placement:

At a practical level it is enough to understand that most pumps are centrifugal, designed to push, not pull water. It is best to situate them at or below water level and as close as practical to the feature to optimize energy use/flow efficiency.

Pumps should be located to provide maximum utility and safety. They should be set/fastened to a solid platform and kept in a level position. See and follow the manufacturers' installation instructions.

Above Grade:

Pumps should be sheltered by at least a cover over the motor to reduce weathering/water damage and water-proof conduit and seal-tight connectors should be supplied for the electrical. Though some shelter might be constructed over the pump for the above reasons and to keep out curious hands, ventilation must be provided for cooling and to lessen condensation.

Dry, emerged pumps are positioned outside of the water feature in a pump/equipment area, vault or room. Vaults are below grade (water-level) and should be equipped with a drain to the storm or sanitary sewer or have their own automatic sump pump with a float switch to avoid flooding and damaging the non-submersible motor and electrical.

Pumps for Filters and other Effects:

Pumps for filters should generally be separate from those used for jets, waterfalls et al.. Reasoning? 1) to provide adequate pressure and volume through the filter 2) & the same for display, aeration and circulation purposes. 3) allow enough force for back-washing cycles where applicable. 4) to prevent "over-driving" your filter(s).

An exception comes with the use of diversion or pressure-control valves with or without solenoids which may be utilized with one larger pump versus two or more smaller pumps. However, in most cases, "spreading out" the pumping by having more than one pump mechanism is advised. The higher operational costs of multiple pumps are off-set by the safety of having to have only part of the system off-line for repair or maintenance.


System curves can be developed from performance curves that are available from manufacturer's and distributor's showing the relationship between capacity, head, efficiency, horsepower, etc. of any pump/application. It is important that you consult with people who can read these curves when selecting a pump for a required condition.

Bring in a line drawing of your layout and some ideas of desired flow rates. This will help your dealer in matching the pump and motor to your system. Improper choice, installation or handling of circulation systems will result in inefficiency, higher costs and early pump failure.


If this brief overview has merely whet your appetite for more technical information, the Pump Handbook by Karassik, Kotzsch, Frazer & Messina through McGraw-Hill is recommended.

See your yellow pages for pump manufacturers, distributors, and dealers, and Waterscape Contractors. Contact them for help and specifications for their lines.

Bibliography/Further Reading:

Aurand, D.C. 1986. Fountains and Pools, Construction Guidelines & Specifications. PDA Publishers Corp., Mesa, AZ

Cuny, Joseph F. 1986. All you ever wanted to know about pumps, & then some. In Practical Koi Keeping Associated Koi Clubs of America.

Fujita, Grant. 1987. Nishikigoi Book. Self-published. p.91,92

Talley, Rod. 1993. Pond plumbing and pump installation hints. Koi  USA 9,10/93.

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

V. 1 Print and eBook on Amazon
V. 2 Print and eBook on Amazon

by Robert (Bob) Fenner
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