Just as your heart is vital for circulating your blood around your body the pond pump is the heart of your garden pond system, it is the mechanism that circulates and filters the pond water. So choosing the  correct size of pond pump is paramount to the health and beauty of your garden pond . Choosing   good and adequately sized pond pumps can sometimes be a life or death decision for your pond fish and the difference between a garden eyesore containing  green stagnant water where fish can barely survive let alone be seen, if they do manage to survive, or a sparkling clean healthy garden pond  with active healthy vivid colorful fish.

Horses for Courses or The Right Pond Pump for your Garden pond

A Koi pond or any garden pond that is a home to pond fish requries that the water be turned (circulated) every one  to two  hours  where as  a water garden containing no fish only needs to be  be turned every 3-4 hours
Adequately sized pond pumps are the  key components of all garden water features.   Stagnant bodies of water are not only unattractive but they become infested with  mosquitoes, which are not only a nuisance, but also a health hazard. Due to the recent outbreaks of the West Nile virus, it is essential  even if you have only a water garden and no pond fish at all that you employ pond pumps that  circulate your garden pond water as mosquitoes do not like moving water.

When shopping for pond pumps, the pond  pump you take home needs to be capable of pumping the volume of water in your garden pond, to greater or lesser extent, the strength of the pump required is   dependent on various factors such as size of pond whether you have fish in your pond or ever intend to house pond fish , whether you garden pond includes streams  waterfalls , fountains and or decorative spitters , filters uv clarifiers.

The first factor to take in to consideration  when shopping for garden pond pump  is the size of your pond. Pond Pumps are sized by gallons per hour (GPH) output at one foot of lift or height. Manufacturers usually provide charts that demonstrate  the power of each size of pond pump according to incremental heights of one foot .Ideally,  pond  pumps  that are used in garden ponds where fish are housed should be able to recycle half your ponds  volume of water  every hour.

In other words if you have a garden pond that holds 1000 galons of water then you need a pond pump that will re circulate at least 500 galons of water an hour(500gph).  This rate of water circulation will assure that your garden pond is a healthy place for plants and pond fish.

To calculate the volume of water in your garden  pond

Multiply the length x the width x the depth x 7.481

example:garden  pond measuring  6′ x 9′ x 2′  x 7.481=  approx. 807 US Gallons

When you know the water volume you can work out the required pond pump output gallons  per hour) considering the purpose of the pond (fish or no fish) as mentioned earlier

* A normal 1000gal water garden  (no fish) will require a pump with  250 GPH output to circulate the water every 3-4 hours
* A normal 1000 gal garden  pond (with  fish) will require a pump with 500 GPH output to circulate the water every 1-2 hours.

Pond pumps get more expensive the bigger the pond and you don’t want to make a costly mistake by choosing the wrong one.

Beware that the addition of even  a small waterfall to a garden pond may alter the size of pond pump you may need . It  takes greater pressure to move water through pipes over a longer distance  and additional power again to move water upward, so  larger more powerful pond pumps may be required. Even in the case of smaller garden ponds if they  have a tall waterfall feature they may require a larger pond pump than bigger ponds with no or smaller waterfalls.  Generally speaking for a waterfall you will need  100 – 150 gph per inch of width of weir (the portion that the water spills from).

For example if you have a waterfall that has an 10 in spillway or weir  and you wish the water to pass over the edge of the spillway at full flow, then you will need a pond pump that passes 125(gph) x 10  = 1250 gph  plus your original 500 gph = new pond pump should be at least capable of pumping  1750 gph .Calculating the proper pond pump size for waterfalls is always  tricky, because you must take into account your waterfall’s height.  To do this , you must measure the vertical height from the top of your pump to the top of your waterfall.  plus, you must add another foot of height or lift for every 10 feet of hose you use to convey the water from the pond pump to the top of your waterfall  (this  allows for Resistance and therefore for loss of volume from resistance within the hose).  To calculate the necessary pond pump GPH, as a  general rule of thumb as stated above for each inch of width of weir will require an extra 100 to 150 GPH ,if you apply this rule when performing your calculations you will not go far wrong but if you would like to perform more specific and accurate calculation please use resistance tables provided here .

The  gph amount figure of your pond pump can also be affected by how smooth or rocky the weir is, the bumpier it is the greater the water pressure needed to force the water to pass through it. If you are happy with  less than a full flow of water over the weir, then you will not need as powerful a pond pump .You should however also  look at the possible water requirements of your pond filter and ultraviolet sterilizer unit if you plan on adding one, it is crucial that you make sure that you are moving the correct amount of water for these pond devices. Take into consideration your filter size.

For the above volume pond I would put in a 1200 gallon filter. I always look at amount in gallons and go one size up more filtration is better than not enough .Look at the circulation of the filter and match your pond  pump to it. It is always better to go for a more powerful pond pump or at least one tailored to meet the water volume requirements of the garden ponds most water hungry device which is usually the waterfall. Water flow ,to devices requiring  less gph  such as the pond filter can always be diverted with the use of a tee junctions but you must be careful not to  exceed the filter circulation to increase your waterfalls aesthetic  appearance , as you will compromise the overall efficiency of your filter water needs to pass at a certain rate across the media in the filter bed in order for the pond water to be cleaned by the pond filter.If you have a waterfall and you find that the discharge from the pond filter is not providing  as pleasing  a display as you would like it is always possible to run an additional smaller pump just to your waterfall to increase the volume of water going over the falls to make it more aesthetically pleasing .

Garden pond pumps come in a variety of configurations, with the most common ones being the submersible type. These pumps are designed to live in the bottom of your pond. The pros are that they are relatively inexpensive and easy to set up. The cons are that they involve a certain degree of maintenance  to keep the pump in optimum working order. Submersible pumps tend to get clogged with debris fairly easily, and if not cleaned regularly, will burn out and need to be replaced often. The second type of pump is designed to live outside the pond. These pumps are usually larger than the submersible ones, more expensive usually need to be hidden from view , but require much less maintenance if you live in a warm winter climate and appear to last  longer than submersible pond pumps.

My last word on the this subject of pond pumps is hopefully to leave you with a handy tip,lots of  Pond pump manufacturers tend to use the  actual output intention in the  name of the pond pump such as “somebodies Eco Filter Pond Pumps (meaning it is both a pond pump and pond filter combined in the same unit)  or similarly  Somebodies Fountain Pond Pumps.is a combination fountain and pond pump  With these type of combination pond pumps its not necessary to make two sets of  individual calculations, as you  would have to do if  you bought them separately. It is not necessary to calculate the output required based on pond volume PLUS the output required to also power the fountain, waterfall or filter, the gph for all has been calculated for you.

I hope this post has  helped you just a little little in adequately determining the proper size of pond pump for your garden pond or water garden.