How Pond Pumps Work

by: Demi Fortuna

The most common pumps in Water Gardening are centrifugal pumps. These use spinning blades or vanes to push water. The way the motor spins the impeller varies, but all centrifugal pumps work the same way. Water entering the front of the pump hits spinning blades or vanes on the face of the impeller which sling water out of the chamber, or volute, at a 90 degree angle, through the outlet and up the pipe.

Pumps are measured by the volume of water they produce, in gallons per hour (GPH) and the pressure they create. Pressure can be measured in pounds per square inch (psi), but is easier to visualize in Feet of Head, the maximum height in feet that a pump can push a column of water. One psi equals 2.31 feet of Head, so a pump with a 23’ Shut-off Head Height produces about 10psi. It stands to reason that it’s easier for a pump to push water a foot high than 10 feet high, so because flows vary depending on the height, pump flow is measured in GPH at given Head Heights, as in ‘1200GPH at 1’ of Head’.

You’ll need to know both the GPH your water garden requires and the head height of your waterfall to choose the right pump. Then you’ll be able to select the pump that gives you the flow you want at the head you need using the pump chart supplied by the manufacturer.