Determine the width of your waterfall, as measured at the point where the water flows over.
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.
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.
Determine the height of waterfall as measured from the surface level of the water to the top of the waterfall.
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.
Things You Will Need
- Measuring tape
- Make sure you read the pump's directions carefully, because some pumps list their size in gallons per minute rather than gallons per hour. To convert gallons per minute to gallons per hour, multiply by 60. For example, 4 gallons a minute is 240 gallons an hour.