External Pond Pumps – Direct Drive Pumps
External Pond Pumps as the name implies are installed outside of the koi pond. They are generally the best suited pond pumps to use for building a koi pond.
That is because external pond pumps can provide greater water flow than most submersible pond pumps. They are also cheaper to run.
External pond pumps are much more reliable than submersible pumps and have a longer life. This is important because your pump needs to be able to run 24/7 without clogging or breaking down.
If they do break down external pumps can be repaired. Because submersible pumps must run underwater the workings are sealed in a waterproof resin. That means when they break, they are essentially throw away pumps and need to be replaced.
There are two basic types of external pond pumps. They are direct drive and magnetic drive. An important consideration when sizing a pump is head height.
External Pond Pumps And Head Height
The amount of lift a pump has is called its head height. As the height a pump needs to lift water increases its output decreases.
If you look at specifications for various external pond pumps you will notice that they are rated at GPH at various head heights.
This is important because a pump that is rated at 4,000 GPH at discharge or 0 head height may only be able to move 2,000 GPH at 10 feet of head. This is referred to as a pumps power curve.
Direct Drive Pond Pumps
Direct drive external pond pumps have the advantage of being able to lift and draw water toward them. This makes them ideal for use in a waterfall where water from the pond must be raised to it or in applications where water needs to be pumped up hill.
They generally will cost more to run than a magnetic pump, but in some situations they are your only choice when high water flow is needed, for example if you have a tall waterfall.
There is a hybrid form of direct drive pond pump that is submersible. This offers you an alternative if you really want your pump out of sight but want to avoid some of the disadvantages of the standard garden pond type of submersible pond pump.
One note of caution if you do decide to buy a submersible direct drive pump. Make sure it is oil free because some pumps will begin to leak and oil as we all know is not good for the water or our fish.
Magnetic Drive Pond Pumps
Magnetic drive pumps are also called mag drive pumps. Usually they are submersible pumps because they operate at very low head heights and can’t draw much water into the pump.
There are some Mag Drive pumps that can operate outside the pond like standard external pond pumps. In situations where you can install them below water level, which is called a flooded suction, they can move a lot of water cheaply. But as head height increases their output falls much faster than a direct drive pond pump.
Mag Drive pumps – Pros And Cons
Magnetic drive pond pumps use an electromagnetic field which turns an impeller. The main advantage of this is they are very energy-efficient and have a long service life.
Mag Drive pumps are also very easy to repair as the only moving part is a magnetic shaft with an impeller attached to it.
Their main disadvantage is in high head applications, where high water flow is required. They are usually more expensive than direct drive pond pumps,but this is greatly offset by their energy savings. In
Generally speaking, if you don’t have a high head requirement, magnetic drive pond pumps may be your best choice. But if you have a tall waterfall or need to move water uphill or a significant distance direct drive external pond pumps would be a better choice.
