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Choosing A Pond Pump: Part 2

What size pump do I need for my pond?

This question’s answer is largely dependent on your needs. As a pond owner, you must decide whether your pump will be used for filtration, used to power water displays in an ornamental pond, or for recirculation. We will outline some of the variables that will affect your choice of pump for each of these functions.

Filtration

In order to filter your pond with maximum effectiveness, its entire volume should be circulated at a rate of once every hour; and at a minimum, its volume must be circulated at a rate of once every two hours. Your pump must be chosen with these concepts in mind. For instance, if your pond were 2,500 gallons, the pump you choose would need a 2,500 gallon per hour (GPH) rating to achieve maximum effectiveness and 1,250 GPH at a minimum. However, it is always better to err on the side of caution by choosing a pump one size larger than the one you calculate for your needs. Remember that a pump’s output may never be increased, but it may be reduced or restricted very easily through the use of a common ball valve. A 3,000 GPH pump may be restricted to only circulate 2,500 GPH, but a 2,000 GPH pump can never circulate more than its rating. Be sure to check the pump compatibility of your filter before making the final decision on a pump. Your filter should list a maximum pump flow set by its manufacturer. Choosing a pump with a flow greater than the filter recommends can jeopardize the effectiveness of the filter and lead to an unhealthy pond. If waterfalls, fountains, or other decorative water features are present, you should consider running a separate pump for that feature or features. This will ensure that your water feature will run consistently despite the status of your filter.

Water Features

Whether your water feature is a trickling stream or thundering waterfall, a pump will be responsible for making it flow. Choosing the appropriate pump for this application is, again, highly subjective and depends upon your personal preference. However, there are some helpful methods of determining what pump will best suit your needs. For instance, for most streams, waterfalls, and features you can approximate the size pump you need by using a garden hose. A standard 5/8” garden hose has a flow rate between 850 GPH and 900GPH. By running a standard garden hose at the source of your stream, waterfall, or water feature, you can get an idea of the size pump you will want. If the flow produced by the garden hose is not as dramatic as you would like your feature to ultimately have, then use it to approximate the flow you would like. For example, if you would like the flow to be about twice as much, then you are looking for a pump with a flow rate of between 1,700 GPH and 1,800 GPH at the given head height.

Head height refers to an approximation of the distance (both horizontally and vertically) through which a pump will need to push water. Every ten feet of pipe through which water will travel horizontally contributes 1 foot of head height (10:1 ratio) while every vertical foot also contributes 1 foot of head height (1:1 ratio). If you were to install your pump 30 feet from your water feature, which was 4 feet above the ponds surface level, your water feature’s head height would be 7 feet (horizontal distance contributes 3 ft and the vertical height also contributes 4 ft).

(Horizontal distance / 10 ft) + (vertical height above water level) = head height

So if you calculated that your stream, waterfall, or feature needs a flow of 1,800 GPH through the garden hose approximation technique and your water feature’s head height is 7 feet, then you need to find a pump whose GPH meets or exceeds 1,800 GPH at 7 feet of head.

For a more precise method of measuring the flow a stream or waterfall will require for a given effect, you may wish to use the following calculations:

Trickle (1/8” deep) =100 GPH per 4” of ledge

Medium (1/4” deep) =100 GPH per 2” of ledge

Dramatic (1/2” deep) =100 GPH per 1” of ledge

For instance, if your stream or waterfall is 24” wide and you would like a trickle, then you will need a pump with a flow that is equal or greater than 600 GPH at the feature’s given head height. You will need a pump with a flow equal or greater than 1,200 GPH for a medium flow and 2,400 GPH for a dramatic flow at the feature’s given head height.

When considering a pump for fountains, statuary, and spitters, be sure that you follow the manufacturers suggested pump flow. Be sure to check the pump compatibility of your features before making the final decision on a pump. Your features should list a recommended pump flow set by its manufacturer. Choosing a pump with a flow outside the feature’s recommended rates will influence the overall look of the feature. If a filtration system is also present, you should consider running a separate pump for the filter. This will ensure that your water feature will run consistently despite the status of your filter.

Recirculation

Circulating the water in your pond will ensure that your pond’s beneficial nutrients are distributed to all aquatic life and prevent pond turnovers or destratification. Using a pump in one or both of the aforementioned applications will result in some recirculation in your pond. Choosing the proper filtration system and pump for your pond will adequately recirculate your pond’s water. Ornamental water displays will help recirculate your pond’s water, but may not always adequately distribute nutrients or prevent turnovers, stagnation, and thermal stratification.

Check out our wide selection of pumps and more at www.bestnest.com. If you would like more personal assistance, please email us at [email protected] or call 877-369-5446.

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