How to Size a Waterfall Pump

If your waterfall pump is not large enough, it won't be able to keep the waterfall going at your desired rate. The size of a waterfall pump is measured in how many gallons per hour it can pump for a given height. The size pump you need is dependent on the width, depth and height of your waterfall. If you are choosing between a pump sightly larger than you need and one slightly smaller, bigger is better, so you do not overstress the pump and cause it to wear out more quickly than usual.

  1. Determine the width of your waterfall, as measured at the point where the water flows over.

  2. Determine the depth of the water you want to flow over the fall. If you want a slow-flowing waterfall, an eighth of an inch should be sufficient. For faster-moving waterfalls, three quarters of an inch is a better depth.

  3. Consult a pump-size chart, available online (see Resources), to determine the number of gallons per hour you will need to pump to keep your waterfall going at your desired rate. For example, if you want half an inch of water depth across a one-foot-wide waterfall, you will need 780 gallons per hour.

  4. Determine the height of waterfall as measured from the surface level of the water to the top of the waterfall.

  5. Select a waterfall pump that provides the necessary gallons per hour at the height for your waterfall. For example, a pump might provide 400 gallons per hour at a height of one foot, but only 340 gallons per hour at a height of three feet. You can find this info on the pump's directions.

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