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How Do I Properly Size a Pump to Create the Waterfall I’m Looking For? – Water Garden Q & A

Picture of a Waterfall

Q: How do I properly size a pump to create the waterfall I’m looking for? – Several Customers

A: We get this question asked to us quite a bit. The following process will help you in determing the correct pump size for a waterfall:

Step 1: Determine the Head Pressure (Head)

Head equals the total number of feet from theCalculating Pump Size Chart top of the waterfall to the water’s surface. For example: Let’s say that height is equal to 5′.

Step 2: Determining Desired Water Flow
In general, you will need 1,500 gallons per hour (gph) for every 1-foot of waterfall discharge for an average flow. The discharge is considered where the water enters back into the pond. For example: Let’s say the width of our waterfall is 2′. This would mean we need a pump of approximately 3,000 gph.

Step 3: Putting It All Together
In our example, our head pressure is 5′ and the approximate gph of our desired pump is 3,000 gph. This means would need a pump that would pump 3,000 gph at 5′ of head.

Other Notes:

  • For a heavy waterfall flow, use 2,000 gph per foot of waterfall discharge.
  • For a lighter waterfall flow, use 1,000 gph per foot of waterfall discharge.
  • If the tubing from the pump to the waterfall is greater than 10′ then it is recommended to add 1 foot of head for every 10′ of tubing.
  • We also have a calculator on our website to help calculate this formula for you. Click here to view the calculator.

4 Responses

  1. I think my math is off. If you need 1500 gallons per foot, wouldn’t you need 7500 gph? Multiplied by 2 would equal 15000 gph. What am I missing?

    • Hi Ernest – There are really 2 different equations at play here and you need to calculate the flow rate separately from the head pressure. If your waterfall is only 2 ft wide you would need 1500gph x 2ft = 3,000gph of flow. The other part of the equation is the head pressure which also has 2 parts, horizontal and vertical. Say the distance from your pump to the waterfall is 20 ft. – this means 20ft/10ft(1ft head pressure for every 10 ft distance) = 2ft head pressure. This is your horizontal head pressure. Then say the height from the surface of your pond water to the top of the waterfall is 3ft. – this means 3ft head pressure (1ft head pressure for every 1ft height). Then you add your vertical and horizontal head pressure together, 2ft horizontal + 3ft vertical = 5ft total head pressure. Now you will need to look for a pump that can provide 3,000gph of flow at 5ft head pressure. This is where the pump flow chart matters. A pump may be listed as a 4,000gph flow but that is without or with minimal head pressure. When you look at the flow chart for 5ft head pressure, a 4,000gph pump may provide only the 3,000gph flow that is needed. I know there is a lot of calculating involved here. If you are trying to calculate a pump for you pond and can provide the width of waterfall, the distance from the pump to waterfall and the height of the waterfall as can help with the calculation.

      • Wow, thanks for the explanation. I am planning my pond and will send you the height once I’ve finished with the idea. This is a very interesting problem and I’m thankful for your time.

      • No problem Ernest, you can always email us directly at pondhelp @ thepondguy.com as well and we will be happy to answer any of your pond questions!

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