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

Enter Pond Size
Click "Calculate your Pond Pump" to reveal pump size for a 90 minute turnover.
Pond Length
Pond Width
Average Pond Depth Depth

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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 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 completly pump the entire pond volume once every 90 minutes. Acceptable pumping volumes is plus or minus 50% depending on fish load, shape of pond and natural weather conditions and temperatures.

Waterfall Flow Calculator
Waterfalls and cascades in ponds and water gardens add circulation, filtration and a lovely sound to the pondscape. Depending on the size of your pond you will want to match the width and flow appropriately so the waterfall is the proper size in comparision to the overall volume of the pond. The following calculators will help choose the proper pump for your waterfall and streambed. A suggested standard for most ponds is 100 gallons per hour for every inch of weir width. Remember it is easier to reduce the flow in your waterfall by adding a ball-valve inline than it is to wish you had more flow from your pump.

Waterfall Weir/Waterfall Width: inches

Desired Flow Depth inches
Enter the flow depth based on the following numbers:

1.5" - 3" = very heavy flow

0.875" - 1.25" = average flow
0.125" - 0.75" = light flow

Your pump should pprovide gallons per hour at the spillway/waterfall/stream start.

Don't forget that this is the flow needed coming through the waterfall and not what is exiting your pump. Ensure to read the pump specifications and verify with the pump curves provided by the manufacturer that the pump has the head capabilities and useable volume to fulfil the needs of your waterfall, pump, skimmer etc. Also note that some specific stainless steel weirs and colored LED lighted sheer weirs have quite different flow volume parameters.

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Ensure the pump you buy has the correct flow rates for your weir width and streambed size and length. It is always adviseable to choose a pump that has a higher volume flow than recommended and then throttle back the flow using an inline ball valve or flow control system.

Pond & Waterfall Pump

To calculate the gallons in your pond you can use the formula Length x Width x Depth x 7.5 or use the
Pond Volume Calculator

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