Picking a Pump

Picking a Pump

Picking a Pump

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Oh No! A Whirlpool!
When choosing a pump for your pond, you first need to consider the size of your pond. The size of your pump should be close to or less than half the volume of your pond per hour or you get a lot of turbulence in the water. To calculate the volume of your pond, use the following formula:

length x width x average depth x 7.5 = volume in American Gallons

Spitting frog or Niagara Falls?
Next, decide what you want the pump to do. For a simple fountain you can just decide how big a fountain you want and read the side of the pump box. If you want your pump for filtering your pond, see the FAQ on biofilters. If you want a pump for a waterfall, use the following formula:

For a waterfall 1/4″ deep:  width of waterfall in inches x 50 = gallons per hour at height
For a waterfall 1/2″ deep:  width of waterfall in inches x 100 = gallons per hour at height
For a waterfall 1″ deep:  width of waterfall in inches x 200 = gallons per hour at height

The depth of your waterfall depends on the look you want. A depth of 1/4″ will give you just a trickle and is not recommended for waterfalls more than 8″ wide. A 1″ deep waterfall will give a nice effect and is recommended for waterfall a foot wide or more. It is possible to have even deeper falls simply by increasing the size of your pump.

But What Does At Height Mean?
Most pumps will indicate on the side of the box how many gallons per hour they will pump at certain heights, usually at least at 3, 5 and 10 feet. (As the height increases, the volume of water decreases… more height, less water). If your waterfall is at some distance from your pond you also may need to consider that every 10 feet of hose adds the equivalent of one foot of height to the pumping requirements.
Putting it All Together
You can either choose a pump, and build a waterfall to fit or build the waterfall and choose a pump to fit. Here is an example of both calculations:

Calculate for a waterfall 3 feet high, 10 feet away from the pond that is 12 inches across and 1/2″ deep.

First, calculate how much water you need.

For a waterfall 1/2″ deep, use: Width in inches x 100
Calculation: 12 x 100 =1200 GPH at height

Then, calculate how large a pump you need.
Since the pump waterfall is 10 feet away from the pond, we need to add an extra foot of height. Therefore we need a pump that will do 1200 GPH at 4 feet.

If we use 1200 gph pump to pump 3 feet tall, and 10 feet away from the waterfall, it will give a waterfall 11 and 1/4 inches wide and 1/2 an inch deep at that four feet of height since it has an output of 1125 gph at 4ft.

Don’t forget that the water will spread out to fill the entire area available to it.

If you are still having trouble calculating the size of the pump you need, bring in your measurements to the nursery and our friendly staff and will help you figure out the pump you need. You will need to know what size your pond is, what you want the pump to do, and, if for a waterfall, the size of the falls and distance from the pond (both vertically and horizontally.)