Having the correct pump is vital to a well-working fountain or pond. A simple calculation to know what the water volume of the fountain or pond is to calculate the length multiplied by the width and times the depth times 7.43 gallons per cubic foot – or L x W x D x 7.43 gallons/cubic foot. But there are many other factors to consider when purchasing a fountain pump for a pond or water feature.

Two pink water lilies 'Marliacea Rosea'  in the foreground of the pond. Blurred cascade fountain in the background. Sunny day.
credit: Marina Denisenko/iStock/GettyImages
How to Size a Fountain Pump

Water Fountain Height Calculation

The water fountain height calculation helps you determine what type of waterfall you want for your feature. A waterfall provides a dramatic aesthetic to the landscaping that buttresses a home. To create a simple waterfall, the gallon per hour that churns from the pump should be 1,500. This will give a discharge of a foot for the waterfall. Discharge is when the water returns back to the source, such as a pond or fountain basin. For a higher waterfall, double or triple the gallon per hour flow to 3,000 or 4,500.

Head Height Help

The head height rating and maximum lift are important in sizing a fountain pump. To do this, first, measure the diameter of the fountain spout. Multiply that number by 100. This calculates the gallons per hour – or GPH. If the fountain spout is 2 inches in diameter, then the fountain has 200 gallons per hour – or 2 x 200 = GPH. Next, measure the height of the fountain. Locate where the pump sits if it has a housing unit that isn't at the base of the fountain. Measure from where the pump will rest to the top of the fountain to where the spout meets the air. This is the head height rating. The head height rating is the measurement needed to know how high the pump needs to be to push the water in order for it to reach the spout and release the water into the waterfall, rock feature or basin. The pumping height is the space between the outlet port on the pump to the surface of the water level.

Water Flow Control

If you want a trickle of water to gently fall from the spout, you will need a pump that measures at just about the same vertical measurement as the head height rating. For a strong flow of water from the spout, choose a pump with a maximum height that is higher than that of where the water emerges. A discharge flow reducer or valve at the spout can offer more control of the water flow for different uses, such as a trickle for everyday relaxation or a splashing torrent for family gatherings where the pleasing sound of the water fountain would otherwise be drowned out.

How to Calculate Water

If you aren't sure how many gallons a pond or fountain can hold, then you will need to figure that out in order to find the best pump to use for your water feature. Measure the length by the width and depth. For instance, if you have a large water feature or pond at 15x10x4, it can hold 600 cubic feet. Each cubic foot holds 7.48 gallons of water. Therefore, the pond can hold a little more than 4,000 gallons (600 x 7.48). A small water pump for an indoor fountain that offers a bit of ambiance in the corner and only pumps out less than 50 gallons is easy to install and doesn't require much calculating. Be sure not to get a pump that is too big for the small water feature or it may spray water up and out of the spout.