How to Choose the Right Pond Pump for Your Unique Needs

How to Choose the Right Pond Pump for Your Unique Needs

Water movement is essential for the health of ornamental fish ponds and water gardens. As discussed in a previous post, water movement aerates the water, keeps particles suspended so the filter can remove them, and brings nutrients to pond plants. 

With a wide array of pond pump options at your disposal, making an informed selection is paramount to achieving your desired water flow and performance goals. In this blog, we will delve into the various types of pond pumps and provide guidance on how to choose the most suitable one for your unique pond.

 

Understanding the Mechanics of Pond Pumps

Let's first delve into the fundamental mechanics of water pumps commonly used in backyard ornamental ponds.

The basic principle behind all pond pumps is to move water from one location to another. This is achieved through a spinning paddle known as the impeller, nestled within the pump. The impeller's rotation draws water in through the intake side of the pump and propels it out through the discharge side. The design and size of the impeller play a critical role in determining the pump's flow rate, pressure, and efficiency. 

Simpler pumps have a straightforward role: moving water. In contrast, more complex designs allow small leaves and other debris to pass through without clogging the impeller. All pond pumps use electricity to spin the impeller and create water flow. Engineers have designed a variety of pump designs based on flow rate and pressure specifications. To make things easy, we’ll focus on the most common types of pumps used on backyard ponds.


The Different Types of Pond Pumps

As mentioned, not all water pumps are created equal. Each design has its own unique advantages and applications. Selecting the right pump is pivotal, as the wrong pump can result in too much or too little water flow, wasted electricity, or cause your pond filter to work poorly. 


Submersible Pond Pumps

Submersible pumps are a popular choice for goldfish ponds and water gardens, especially in smaller to medium-sized setups. These pumps are designed to be placed underwater, typically near the pond's bottom. Water is drawn into the pump and forced under pressure out of the pump’s discharge outlet. 

Submersible pumps are versatile and can be used for water circulation, powering pond filters, fountains, and water features. They're easy to install, low-maintenance, and relatively low cost. These pumps simply plug into an electrical outlet. No special wiring is necessary. Submersible pond pumps can be broadly classified into two categories, each tailored to specific preferences and requirements: 

  1. Mag-drive water pumps
  2. Direct drive water pumps

 

Mag-Drive Water Pumps

Most small pond pumps are classified as magnetic drive pumps, often referred to as “mag-drive.” The impeller has a drive magnet surrounding it. When the pump is plugged into an electrical outlet the magnetic field created inside the pump causes the impeller to spin and pump water. 

This straightforward design can easily be adapted to create a range of pump sizes including tiny table-top fountain pumps. 

 

Direct Drive Water Pumps

These pumps use a direct drive system rather than a magnetic drive. Direct drive pumps have a mechanical connection, typically in the form of a drive shaft, which links the electric motor and the impeller. 

In this configuration, the electric motor rotates the impeller, generating centrifugal force that drives the movement of water through the pump and into the discharge line. The advantages of direct drive pumps include their robust power, resistance to clogs, and the ability to allow solids like leaves and algae to pass through. 

Pro Tip!

  • Submersible direct drive pumps prove particularly effective in scenarios involving tall waterfalls, streams, or when water must be pumped over longer distances from the pond. 
  • Submersible magnetic drive pumps are best when the desired flow rate remains under 3,000 gallons per hour (gph) and the head height does not exceed ten feet. 

 

External Pond Pumps

For large water gardens and koi ponds that have more extensive water features like large waterfalls, streams, or advanced filtration systems, external direct drive pumps are the go-to choice. They are installed outside the pond, often a great distance from the pond. 

External pond pumps are modeled after swimming pool and spa filter pumps. They will use more electricity and create motor noise, but that is the tradeoff when you need a high-powered water pump. You’ll have to have an electrician run the power line from a circuit breaker to the pump location.

 

Small pond with a water fountain

Key Considerations in Selecting Your Pond Pump

For the majority of DIY pond projects, a submersible magnetic drive pump is typically your go-to choice. However, when making this selection, there are several crucial factors to keep in mind. First and foremost, you need to determine the necessary flow rate to operate your filter, waterfall, or fountain effectively.

Let's focus on pond filters for a moment. These essential components come with a recommended flow rate, which represents the maximum gallons per hour (gph) that the filter can effectively handle. Pump manufacturers often display the pump's flow rate on the packaging. While these numbers may seem impressive, they often prove less useful in real-world pond applications. 

The reason is that the maximum flow rate is typically calculated under ideal conditions, with the pump submerged in just a few inches of water and without the added resistance of a filter, tubing, or a fountain head. In reality, the flow rate of a submersible water pump varies due to a phenomenon known as "head pressure."


Demystifying Head Pressure and Flow Rate for Pond Pumps

Head pressure is a crucial factor to consider when selecting a submersible pond pump. Head pressure refers to the resistance or pressure that a pump must overcome to move water from its source (a pond) to its destination (such as a waterfall or filtration system). It is measured in feet or meters of “head” (or head of water). 

Here's the key: the greater the vertical distance the water must travel, the higher the head pressure. The higher the head pressure, the lower the water flow. To illustrate this, let's look at a pump flow rate chart below.

pump flow rate chart below

To put this into perspective, let's take "Model 2" of a pump, which boasts a flow rate of 360 gallons per hour (gph) when there's no head of water to overcome. Now, imagine attaching a fountainhead to this pump, positioning it about a foot above the water's surface. In this scenario, the flow rate would decrease to 270 gph.

However, consider what happens when you connect a piece of tubing from the pump to a small waterfall roughly three feet high. To achieve this, you'd need approximately five feet of tubing above the water level. The result? A significant reduction in the flow rate to a mere 80 gph.

This example clearly illustrates how the advertised flow rate of 360 gph drops to 80 gph when the pump is utilized for a waterfall. The most common mistake pondkeepers make when shopping for a water pump is overlooking the impact of head pressure. Using an underpowered pump in your pond project means you won't have the necessary water flow to operate a filter, waterfall, or any other water feature.


Calculating the Ideal Flow Rate for Your Pond Project

So, here's a quick guide to calculate the flow rate you truly need:

  • When calculating head pressure, only the height above the water level counts. 
  • Use the flow rate chart provided by the pump manufacturer to determine the actual flow rate for your application.
  • Match the pump flow rate to the recommended flow rate for your filter.
  • If a waterfall is part of your plan, measure the height above the water level and add a few extra feet to account for twists and turns in the tubing. These curves introduce friction, which reduces water flow.

 

Large pond with a water fountain

Conclusion 

In your journey to understand pond pumps, you've learned that choosing the right one is vital for your pond's health. Water movement is the lifeblood of your ornamental fish ponds and water gardens. Armed with this knowledge, you can now pick the perfect pump to create a thriving aquatic ecosystem.


Final Takeaways:

  • Most small to medium-sized backyard ponds can use submersible mag drive pond pumps.
  • Large ponds and tall water features require a powerful, high-flow direct drive pump. 
  • Assuming you have selected the proper sized filter for your pond, select a pump based on the filter manufacturer’s recommendations.
  • Always base the pump’s flow rate on the pump manufacturer’s head pressure/flow rate chart and your application’s head height.
  • Many pondkeepers opt for the next largest pump to ensure they will have enough flow. Some pumps come with a flow adjustment valve so you can throttle back the output if necessary.
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