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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.

8 Responses

  1. So if I have 10 feet from pond to waterfall, and my fall is 10 ft wide, That means I would need 30,000 gpm is that right? also can I get that much through a 2 inch line and how big of pump hp.? Thanks

    • Hi Steve – If your waterfall is really 10ft wide you would be in the range of 15,000gph – 25,000gph of flow depending on how heavy you want the waterfall. This would require larger than 2″ line or multiple pumps and multiple waterlines. The 10′ distance from the pond to the waterfall would be head pressure, in this case less than 1′ and would really have no impact on the size pump needed.

  2. You have such a wonderful website…but I’m still having difficulty….My house has a stone chimney with a waterfall built in with a small maybe 10 gallon pool at base. The discharge tube is a half inch in diameter at about ten feet up. Which of your pumps would work best for this application. Any suggestions would be helpful. Thanks

    • Hi Carolyn – The MagFlo pumps would work well but you would need to use at least the 1340 pump if you need to push the water 10ft high. This had a 3/4″ discharge that would need to be stepped down.

  3. 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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