Pumps! No, I'm not talking about your mother's shoes; I mean the mechanical devices used to move water. No doubt, if you have a pond you know a pump is necessary to circulate water. But what are the options available when buying one? What type (External or Submersible) will best fit my needs? How big does a pump need to be? These questions may scare new pond owners. When it comes to choosing the correct pump however, the only thing you need is some basic information.
A pump is a device used to move liquids from lower pressure to higher pressure by adding energy to the water system. They push the material (in this case being water) by lifting or by the force of compression. Basically it is a machine needed to keep water in your pond moving, and/or push water up to your waterfall. It is necessary to aerate your pond and to avoid stagnate or putrid water.
All pumps used in ponds will fall under two categories: external or internal/submersible. An External is used out of water like the systems used for a pool or spa. Internals are used fully submersed in water. Both types have advantages for the buyer.
External pond pumps, not to be confused with External pool pumps that consume energy, are often used in larger ponds. The reason being they are highly energy efficient. This is because they typically use fewer Amps than an Internal/ Submersible pump. An Amp (Ampere) is a unit of electric current. The less Amps used, the less energy used, resulting in more money saved. They are easy to clean with out getting wet, and hook-up to a bottom drain is fairly simple. Also, most come with a leaf trap to reduce clogs. The down side: They are complicated to install and are typically more expensive.
How do External pumps work? Like any pump, two gears turn in and out of the mesh to cause flow. The difference between Submersible and External pumps is that Externals use identical gears. One gear is driven by a motor which in turn drives the other gear. They are both supported by a shaft. The rotating gears create pressure and push the liquid through the discharge outlet.
Internal/Submersible pond pumps are most commonly used in water gardens and Koi ponds. They typically range from 50gph to 50,000gph. They are quick and easy to install. You simply place the pump (fully submerged) in water, plug it in, and attach a hose to any waterfalls you might have. They are space efficient and easily hidden to make for a more natural looking pond. The down side: They can be energy hogs for larger ponds, and replacement parts may be difficult to come by.
How do Internal pumps work? Internal pumps also use two gears. As the gears rotate in and out of the mesh, voids are created and liquid flows into the cavities, the liquid then is forced through the discharge outlet.
So which type of pump best fits your needs? Ask yourself: How many gallons of water are in my pond? What is my budget? Do I mind seeing my pump or would I rather a more discrete approach? Do I prefer easy installation? How many amps do I prefer to run? After taking these questions into consideration, decide which type would suit your pond needs best. There a couple of factors needing consideration before shopping.
First, you need to figure out how many gallons of water are in your pond. To do this, use a simple formula: Average Length x Average Width x Average Depth x 7.48. For example: to find the gallons in a pond that is 10' in length by 6' in width that is 2' deep you would use the formula 10 x 6 x 2 x 7.48 =897.6 or approx. 900 gallons. You want a pump that will circulate the total volume of the pond once per hour. So a pump that is 900gph (gallons per hour) or 15gpm (gallons per minute) would be needed. However, streams, and waterfalls need to be taken into account as well.
If you have a waterfall, you want a pump that can account for the height of the waterfall plus the volume of the pond. If your waterfall is 5' high, and the depth of your pond is 2', the max head (the height) the pump needs to be able to create has to be at least a couple of feet higher than your waterfall or 7'.
To sum things up, if you have a pond that is 900 gallons in volume with a waterfall that is 5' high, you need a pump with a gph of 900 and a max head/height of at least 7'. How will you know what pump is capable of what actions? Do not worry; most pumps come with a ready-made flow-rate chart on the packaging. If you happen to find that one pump that doesn't, as is my luck, simply ask a sales associate. After all, they are there to help.
Once you figure out what type and size pump you will need it's time to go find the right one. Pay close attention to the time allotted for the pump warranty. Most pond pumps are warranted for two-three years. Once you've bought a pump make sure to read the directions (yes, the directions) for easy installation. Pump shopping is not as difficult as it seems.