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Pond & Waterfall Pump Calculator
How to calculate the size of pump you need for your pond

Choosing the right pond pump is a very important. If your pump is for a pond filtration system with a skimmer you will want to ensure your pond has a complete turnover at the correct rate. The filtration requirements, the number of fish in the pond and the BOD (biological oxygen demand) will play a part in calculating in how often you want to pump your full volume through the filtration.

The time it takes for the complete volume of your pond to be pumped is called the turnover. Generally a pond should have a complete turnover every 30 minutes to every 3 hours. Smaller ponds need a complete turnover approximately every hour and larger ponds can handle a turnover rate of up to 6 hours or more depending on aeration in the pond, fish density and other natural conditions. Decorative ponds and koi fish ponds have different requirements so it is best to do research on the baste rate for your particular pond and fish load.
 An acceptable pond pump flow rate is to have a complete turnover every 1.5 hours.


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Pump Should Pump Approximately Gallons Per Hour*

*The total is based on a complete turnover of the volume of the pond every 90 minutes. Actual requirements may vary on pond variables.

When choosing your pump, make sure the gallons per hour is the total at the dynamic head of your pond system. Having long lengths of pond hose with waterfalls and runs of tubing through filters will impact the total gallons that are actually pumped through your system.

Use a large inner diameter pond hose, preferably the same size as your pump outlet to avoid friction loss in the pipe from water flow. Add 1 foot of head for every 10 linear feet of hose in your system. Also include the total head which is the height differential between the surface of the water and the highest point of your pond tubing or outlet, ie: waterfall outlet. Every 90 degree plumbing elbow and T-fitting will also add about 6 inches of head to the equation.

The above calculation is to completely pump the entire pond volume once every 90 minutes. Acceptable pumping volumes is +/- 50% depending on fish load, shape of pond and natural weather conditions and temperatures.