Waterfalls are a popular landscape feature, and the availability of reasonably priced kits are making them easier than ever for homeowners to install. But it can be confusing to figure out what size pump you need, since every waterfall is unique. There are several things to know that will help clear up some of the mystery.
A waterfall pump should have a flow rate that will let it pump approximately half of the pond's volume in one hour. So the first step is to find out how much water your pond holds. If you have not installed a pond yet, and are buying a kit, you can tell easily by checking the kit's specifications. Alternatively, you can measure and do some calculations; the volume of a rectangular object is calculated by measuring three dimensions and multiplying them together. Your pond is probably not rectangular, so you can calculate the surface area of the top, and multiply that by the average depth. Then divide the volume by two and that is the approximate flow rate you want for your waterfall pump.
Head pressure is a bit harder to understand. It has to do with the total maximum vertical height to which a pump can pump water. Measure the vertical height of your waterfall. But don't choose a pump that has a maximum head, also called maximum total lift, that is equal to your waterfall's vertical height. At its maximum head, a pump is not pumping at the flow rate you will be happy with, so you want a pump that has a higher total lift than your vertical height. Also, you want an even larger total lift if your water line has one or more right angle bends in it because these reduce the water pressure in the line.
Cost of operation
If you want to run your waterfall all or most of the time, consider the cost of operating it. This should be listed on the package or product description, or it can be obtained from the manufacturer's website. Running the pump will add to your electric bill, and you may want to understand how much your bill will increase.
Skimmer vs. filter pump
If you have a pond, you ideally should have two pumps -- one pump to circulate the water and run it through a filter or skimmer if you have one, plus a separate pump for your waterfall. It's important to understand the difference between the two kinds of pumps. Get a pump made for the correct purpose to obtain the best results.
Waterfall pump vs. sump pump
If you're making a homemade waterfall, it may seem that a sump pump would function well as a waterfall pump and may save you money. However, don't be tempted to use a sump pump. These kinds of pumps are not built to run all the time and will use much more electricity if you use one for a waterfall, compared with a waterfall pump. Also, if you run a sump pump continuously, the motor may burn out, since they're not meant to be used that way.