Finding the right pump for a water feature can be a challenge, and the stakes are high. The right pump, delivering the right flow at the right head height, while at its best efficiency range, will last and last. Specifying the wrong pump or plumbing can damage the pump, increase operating costs, shorten pump life and lead to pump failure, perhaps even a fish kill if the water feature happens to be a fish pond.

In order to properly size the pump for any water feature, you’ll need to know both components of the work it has to do, the flow and the pressure. The flow is the volume of water it can push in a given time, measured in gallons per hour (GPH). The pressure is the force required to push that flow through plumbing and up to the top of the water feature. We measure pressure in ‘feet of Head”, because it’s easy to visualize. A waterfall four feet high requires the flow be delivered at 4 feet of “Vertical Head”, plus the extra work required to push that flow through the plumbing, the “Friction Head”. The total pressure required is the “Total Dynamic Head” (TDH) of your water feature. Once you know the GPH and the TDH, you can plug them into the Comprehensive Pump Chart (Chart C) to find the right pump.

Follow the steps below to calculate TDH and find the perfect pump for your water feature.

Locate the recommended flow GPH (from step 2) and the diameter of the tubing you will be using in your project to find the corresponding friction loss.

Friction loss is listed here for every foot of tubing length used in your project.

Example: For a recommended flow of 3,000 with 2" tubing, the chart shows friction loss of 0.05. In this example project, we will be using 20' of tubing, so the loss here would be 1.

Located the fitting types that will be used and the fitting size. The corresponding number is the fiction loss per connection as a calculation to the equivalent if that fitting was a straight piece of tubing. For applications with multiple connections, add all corresponding values.

Example: For this project, we need one standard elbow 90°, one male to female adapter, and one swing check valve. All are 2" in diameter, so 8.5 + 4.5 + 19.0 = 32

Calculate total equivalent tubing length

Combine totals from step 3 and 4.

Vertical head is the height in feet from the surface of the water the pump will be sitting in, to the highest point the water is pumped to.

Find the total dynamic head at the top of this chart, then find the pumps below that provide at least that recommended flow. Grey colored cells indicate that the total dynamic head is outside the pump’s operating range and the pump will likely not last in this application. The light blue cells indicate the pump is operating within its operating range. Dark blue means the total dynamic head is in the pump’s best efficiency range, where the pump will run best and longest. If the chart gives you a choice of more than one pump, check for the type that best fits your application, then check for the lowest wattage, to save on operating costs.

All pumps have an optimal range of flow, measured in GPH, and pressure, measured in feet of Head. Pumps operating within their Recommended Operating Range will run better and last longer. Pumps forced to run outside their operating range will tend to fail sooner. Every waterfall needs a certain amount of flow at a certain amount of pressure to achieve a desired effect. Knowing the feature’s Recommended Flow in GPH, and its Total Dynamic Head in feet, lets you select the right pump, running in its optimal range, providing the desired flow at the right head.

Take what you pay per kilowatt per hour, multiply that by the wattage of the pump and divide by 1000.  For the monthly cost, multiply the hourly cost by 720, 24 hours per day times 30 days in a month.

Cost per hour = $          kW  x         Watts ÷ 1000 =           x 720 =         Cost per month

Example: Electric costs $0.10 per kW, the pump draws 100 Watts, so $0.10 kW x 100W ÷ 1000 = $0.01/hr x 720hrs/mo = $7.20/month