Selecting a Pond Pump: How to Calculate Head Height & Flow Rate Title

The wrong pond pump can turn a promising water feature into an eyesore. But the right pump can highlight your pond's best qualities, improve water appearance and clarity, and create a breathtaking feature. Read on to find the best pond pump for your water garden.

Before choosing a pump for your pond, you must determine what you would like its function to be in your pond. Is the pump simply going to circulate your pond water? Do you need a small pump to spray water out of a spitter? Does the pump need to pass your pond water through a UV sterilizer or other type of pond filter? Maybe your pump must support the flow of an impressive waterfall. Whatever your function, there is a perfectly-suited pond pump out there for you to use.

Below, we will explore how to determine your pond's head height and how to determine the flow rate that you will require.

pond pump calculations

Calculate Head Height

  1. Fountain - The distance in feet from the pond surface to the top of the water fountain head.

  2. Waterfall - The distance in feet from the pond surface to the top of the waterfall

  3. Hosing - Add one foot of head height for every 10 feet of hosing, and for every 90 degree curve.

Finally, take all of the values from the steps above and add them together. This will give you the total head height (Step 1 + Step 2 + Step 3 = Total Head Height).

 

Calculate Flow Rate - Gallons Per Hour (GPH)

1. Calculate Pond Volume

Square or Rectangle Ponds

Length (ft.) _______ x Width (ft.) _______ x Depth (ft.) _______ x 7.5 = _______ Gal ÷ 2 = _______ GPH

Round Ponds

0.785 x Top Diameter (ft.) _______ x Bottom Diameter (ft.) _______ x Depth (ft.) _______ x 7.5 = _______ Gal. ÷ 2 = _______ GPH

 

2. Required Flow for Waterfall

The flow rate required for your waterfall depends on how much flow you want. For a steady flow, follow the calculation below.

Waterfall Width _______ inches x 75 (GPH)

 

3. Total Flow Rate = flow rate required for pond volume + flow rate required for waterfall

 

Selecting a Pump

Once you have discovered the proper flow rate required and the head height of your features, you can start looking for the right pump. Each pump will have different flow rates at different head heights, so examine each individual chart. Look for the flow rate at the specified head height that you require.

TIP: Selecting a pump that has slightly greater capacity than your initial needs eliminates the need for upgrades should your plans change. (Just one...more.