Water Garden Pump: What is The Right Size?

Water Pump

Many water garden enthusiasts enjoy the relaxing gurgle of a well placed water feature.  Whether a fountain or water fall, the trickling of water adds an additional calming effect to your water garden. Along with the aesthetic reasons for moving water, there is also the fact that t is essential that you keep the water healthy.  Adding a pump will evenly distribute the oxygen levels and other nutrients in your water garden helping to ensure a healthy ecosystem. There are many factors that go into determining which water pump will meet the requirements for your water garden.

Water garden pump: what is the right size? The right size of water pump needed for your water garden is determined by three factors:

  1. The amount of water you want to pump.
  2. The size of spillway if a waterfall.
  3. The height of how up to you will need to pump the water.

We will go through how to find this information and ultimately determine which pump will be the best for your situation. One thing to keep in mind:  Whatever system you end up deciding on, be sure to purchase a reliable pump that is able to run 365 days a year. Since pumps impact the ecosystem within a water garden, a pump failure can cause water imbalances and endanger your fish or other life in your pond.

Choices Choices So Many Choices…

Before we get into figuring out the size of pump you need, lets take a few moments and  discuss why water pumps are important for your water garden.  First the pump can provide aeration for the plants and fish that you place in your garden. The pump will also keep the water in your garden from becoming stale and foul smelling.  An additional benefit of having a pump is that mosquitoes do not lay their eggs in moving water.  Reducing the mosquito population in your back yard is always a good objective.  

There are several types of water pumps each with their own advantages. When choosing a pump to purchase, ensure to choose a pump with the flow rate of at least half the volume of the water in your water garden.  For example, if you have a 2,000 gallon water garden, your pump should have a minimum flow rate of 1,000 gallons per hour. However, if your water garden has fish, you should select a pump that will circulate the total volume of your water garden every hour. You can classify the type of pump you will need based largely upon how big your water garden is.  If less than 1,000 gallons then a submersible pump will work great.  Submersible pumps are typically rated in gallons per hour.  In larger water gardens an external pump will work better and they are typically rated in horse power. 

Important Terms

There are a few terms that will help you understand what is needed in determining which pump will meet your requirements.

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 your pumping.

Flow rate for water falls – A rule of thumb is that for every 100 gph at the discharge point creates an inch in width.

light flow = 50 gph x waterfall’s width (in.) 

Average flow = 100 gph x waterfall’s width (in.) 

Strong flow = 200 gph x waterfall’s width (in.)

Head height – The distance of elevation from the water garden surface to top of the fountain head above the water garden. Ensure that your pump can achieve the amount of water flow required at the height of your water feature.  As you increase the elevation of your water feature, the pump will have to work harder to push the water to the higher elevation. Typically pumps will have a chart that show what their flow rate is at different head heights.  

Classification and Application of Pumps

Like most products on the market today, there are as many choices as there are applications.  For us the consumer, we have a wide variety to choose from.  As with many products, there are many type of water pumps. 

For the purpose of this article, we will classify water pumps into two categories:  submersible and external.


As you may have guessed from the category, a submersible pump is installed and operated beneath the surface of the pond.  Though obvious, it is important that you only operate the pump submerged.  There a several advantages, One advantage is that because the pump is submerged, any sound they make is greatly reduced. Typically, submerged pumps are used for pumping 1,000 gallons or less.  The main advantage of a submersible pump is that it prevents pump cavitation, a problem associated with a high elevation difference between pump and the fluid surface. Submersible pumps push fluid to the surface as opposed to jet pumps having to pull fluids. Submersibles are more efficient than jet pumps and also do not require priming.  

A couple of safety tips. Water provides the cooling for the pump.  Be careful not to run the pump outside of water as it may burn out.  Also, ensure that you are using your pump on a “ground-fault-interrupter (GFI) plug to ensure electrical safety.


External pumps for your water garden are typically for larger gardens that may have one or more water features.  There are advantages and disadvantages to having and external pump. Lets take a look at the advantages first. 

As an external pump sets outside of the water, access to the pump is usually easier and therefore makes maintenance easier to perform. Since most water gardeners select external pumps for their larger water gardens, the external pumps can be more energy efficient for their size and therefore save significant energy costs over the lifetime of the pump.

There are a few disadvantages to having an external pump.  One is that as the pump sets outside of the water environment, gardeners typically have to build an area where the pump is disguised to match the gardens appearance.  Also also the pump should be placed in a location that can be kept out of inclement weather. 

Depending on where the pump is located, you may have to prime the pump.  Priming the pump entails clearing out air within the pipes that may be between the water garden and the pump.     

The most widely used pumps used in water gardening are Magnetic Drive pumps.  Magnetic drive pumps use an electromagnetically driven impeller to circulate the water.  They require very little maintenance and often last 10 years or longer. One disadvantage is that the pump 

We will also the types of water pumps and the advantages and uses for each.  

Types of Pumps

Magnetic Drive Pumps

Magnetic drive pumps are energy efficient and require very little maintenance. To pump water, the impeller uses electromagnetism, forcing water through the pump. This type of pump is generally used for waterfall effect or for ornaments. It is important to ensure that the water is filtered prior to entering the pump as debris can clog the pump.

Statuary Pumps

To create a small fountain, this is the most suitable pump. It has low head pressure, which means that water forced out will not rise very high.  Rates as high as 320 gph and head heights up to 5.5 feet are available. This type of pump is used for decorative purposes rather than to aerate the water.

Solar Powered Pump

Compared to conventional pumps, solar pumps can be both external or submersible. The difference from conventional pumps, as the name implies, is that they are powered by the sun. Thus they are environmentally friendly and safe to operate.  If your water garden does not have electricity available, a solar pump may be a great fit for your situation as no external electricity is involved. The disadvantage with this type of pump is that it is limited to sunny environments.  If the sun disappears then your pump quits working.  Adding a rechargeable battery to your solar circuit can resolve the sun issue but adds additional expense to your pump.

Related Questions

How does a pump aid in water quality? Circulating your water provides helps to provide oxygen for both plants and fish. Additional water circulation ensures better filtration to help keep the water clear. 

Are pumps required is your water garden has fish? Basically, the answer is yes.  It is important to aerate and filter the water if fish are involved.  Water gardens that are built with the correct plants and fish may forego pumps.  However, it is much easier to maintain a clean water garden with a pump. 

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