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How To Select A Pond Pump

How To Select the Right Pond Pump

Choosing the right pond pump can be a bit confusing, there are many models and brands to choose from nowadays, how do you choose? Although the initial purchase price is usually the main consideration when buying a pond pump, there are a few other more important aspects to bear in mind.

Here are some factors that you may want to consider when purchasing a pump for your pond or waterfall.

    • Pond Size
    • Dynamic Head Pressure
    • Waterfall Width (and desired look)
    • Operating Cost / Energy Efficiency
    • Warranty
    • Price

 

How To Select A Pond Pump

Pond Size

The size of your pond is critical in determining what pump to buy. Too small a pump will cause poor circulation and stagnant area in the pond leading to low oxygen levels, sludge build-up and poor water quality. These factors result in an unhealthy pond and in turn unhealthy fish. Your pump should circulate the volume of your pond a minimum of once very 2 hours, ideally once per hour.

Example:

  • If you have a pond that is 1000 gallons, the minimum pump size is 500 GPH (gallons per hour). If you have quite a few fish in your pond (like most of us) more circulation is better, therefore ideally you should pick a 1000 GPH pump or larger.
 

Dynamic Head Pressure

Dynamic head pressure sounds technical and complicated but for the purposes of selecting a pond pump we don’t need to get too precise, and in if you have a small pond or don’t have a waterfall or stream, then you can ignore it. Basically, dynamic head pressure is all the back pressure that is put onto the pump while it is forcing water through the tubing up to your waterfall, stream or filter. This includes the height of your waterfall, length and diameter of tubing, fittings such as elbow and ball valves, etc. The more dynamic head pressure – the less flow you will get out of your pump.

Key Points to Consider:

  • Waterfall Height – measured in feet from the surface of the pond to the top of the waterfall
  • Length of Tubing – total length in feet from the pump to waterfall or filter. Every 10 feet of tubing adds 1′ of head to the dynamic pressure
  • Number of Fittings – number of 90° elbows and reducing fitting used. Every 90° elbow or reducer fitting adds 1′ of head to the dynamic pressure

Example:

  • The height of your waterfall is 6′, there is 37′ of tubing between the pump and the waterfall and 3 elbows were needed. Add up all of these factors to find out your Dynamic head Pressure.

 

6′              Waterfall Height Factor
3.7′          Tubing length Factor (37/10 =3.7)
3′           Number of Fitting Factor
12.7′

The result is 12.7′ of Dynamic Head Pressure (Round up to 13)

What does this all mean? This means that although the waterfall height is only 6′, if you want 3600 GPH flowing over your waterfall you will need to buy a pond pump that provides 3600 GPH at 13′ of head, not just a pump that provides 3600 GPH. Most pumps are sized according to their flow rate a 0 or 1 ‘ of head. A 3600 GPH pump might only be provide 2000 GPH or less at 13’ of head. Most pump manufactures provide a flow chart for their pumps at varying heights so you know exactly what the flow rate will be at youre desired head height.

Waterfall Width

If you have a waterfall, getting the proper flow of water over it and achieving the right ‘look’ is essential. A small pump on a large waterfall results in the water just trickling over the rocks, which is great if that is the desired effect. However if you are looking for a gushing flow (a miniature Niagara falls) then a larger pond pump is obviously necessary. But how large?  The size of pump you need really depends on the look you are trying to achieve and the width of your waterfall.

A general rule of thumb is to calculate a set flow of water (in GPH) for every inch of width of water at the top of your waterfall. Sounds a little complicated, but it is really quite simple to figure out.

  • 100 GPH per inch of waterfall = somewhat more than trickle
  • 150 GPH per inch of waterfall = medium flow
  • 200 GPH per inch of waterfall = strong flow

 

All you need to do is measure the width of your waterfall (in inches) and multiply that by 100, 150, or 200 depending on the  look you are trying to achieve.

For example

If your waterfall is 10” wide and you want a trickle – do the following calculation -10 (inches wide) x 100 (GPH per inch) = 1000 GPH pond pump

If your waterfall is 18″ wide and you want a strong flow – do the following calculation -18 (inches wide) x 200 (GPH per inch) = 3600 GPH pond pump

Operating Cost

This often overlooked factor often determines the real cost of a pump. Pumps should be running 24 hours a day except in winter, if you have an older style pump that is a ‘direct drive style’ it can significantly affect your electricity bill.

Lets compare 3 pond pumps:

  1. A Leader 3600 GPH direct drive waterfall pump uses 650 watts, and costs $299.99
  2. An AquaSurge 4000 uses 215 watts, and costs  $383.99
  3. A Tetra DHP 4200 Debris handling pump uses 232 watts and costs $329.99

PUMPLeader 3600Aquasurge 4000Tetra DHP 4200
PRICE$299.99$383.99$329.99
FLOW RATE3840 GPH3947 GPH4235 GPH
WATTS650215232
OPERATING COST (per year)$351.36$125.90$135.86
OPERATING COST AFTER YEAR 2$702.72$251.8$271.72
OPERATING COST AFTER YEAR 3$1054.08$377.7$407.58
ACTUAL COST OF PUMP AFTER 3 YEARS$1354.07$761.69$737.57

*Based on 8 months operation per year (April through November) @ $.10  per Kilowatt hour

RESULTS:

As seen in the table above, the operating cost of a pump has a great impact of the overall cost of ‘Owning’ a pump. the Leader pump is less initially expensive to purchase, but costs much more to operate (almost double the operating cost)  than either the Aquascape Aquasurge or Tetra DHP pumps

Pump Warranty

Obviously, pond  pumps with longer warranties are preferable. This means the manufacturer stands behind the product and generally  it is going to provide you with years of dependable service.

Price

As pointed out in the Operation Cost section above, the purchase price is only a small part of the actual price of owning a pump. With a little homework, you can make an informed choice before purchasing a pump.

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