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How to Choose the Correct Size Pond Water Pump

Grainger Editorial Staff

Choosing a pump for your pond or fountain is an important step to ensure you maintain proper water movement. Failure to keep the water properly circulated can result in stagnation, algae buildup and mosquitoes. If you have fish, plants or other aquatic life in your pond, it is essential that you keep the water healthy by evenly distributing the oxygen levels and other nutrients.

Types of Pond Water Pumps

There are two main types of pond water pumps: submersible and external (out-of-pond), also known as centrifugal pumps. Depending on the application, each pump offers specific advantages.

Submersible Pond Pumps

Submersible pumps are designed to be fully submerged underwater at the deepest part of the pond. They are placed directly into your pond or in a skimmer box or pond vault. Submersible pumps range in size from 50 to 5,000 gallons per hour. They are easy to install and are sometime a more economical solution for smaller ponds (up to 1000 gallons of water).They are also quiet and can also be used to drain your pond. If you have fish or other aquatic life in your pond, you may want to consider a model that does not use oil because there is a danger of the pump seal breaking and oil coolant leaking into the water.

Centrifugal Pond Pumps

External or centrifugal pond pumps are a reliable, energy-efficient option. They are installed in a dry location near your pond. External pond water pumps are suitable for larger ponds (over 1000 gallons). Compared to a submersible pump, they are typically louder and more complicated to install, however they are easier to maintain.

When selecting a pond pump, it’s important to keep in mind that pumps have different cord lengths. Make sure the cord is long enough to go through the pond and plug in far away from the water. Some electrical codes specify that the outlet for water features must be at least 6 feet away from the water. It is recommended that you avoid using an extension cord. However, if you must use one, make sure it’s suitable for outdoor use and plugged into a ground fault circuit interrupter (GFCI), so that it will immediately shut off if there is an overload.

How to Size a Fountain or Pond Pump

Pond pumps are sized by gallons per hour (GPH) at one foot of lift or height. Larger capacity pumps are rated by horsepower (HP). To determine the size pond pump, first you need to calculate the volume of water in the pond. To calculate the volume of water in gallons, simply multiply the length x width x average depth x 7.5.

Water Circulation Factors

It is recommended that pond water is circulated at least once per hour. For example, if you have a 500 gallon pond, you need a pump that runs 500 gallons per hour at the height of the discharge. If your pond has a pressurized filter, you ideally want to turn the water approximately once every two hours. For example, if you have a 1000 gallon pond, then you need a pond pump rated at a minimum of 500 GPH. If your pond has a skimmer or waterfall, the water should be turned approximately once every hour. Therefore, if you have an 1800 gallon pond, you will need an 1800 GPH rated pump.

Calculating Head and Lift Height

Two of the most important measurements in sizing a pond or fountain pump are the maximum head height rating and maximum lift. Head height means the vertical height the pump raises water above the surface of the pond. The top height the pond fountain pump can lift the water up to is called “Maximum Head” or “Max Head”. The “Head” is measured straight up from the water level of the pond. Any horizontal/diagonal flow is then measured by its length and 1’ of “Head” added per 10’ of horizontal/diagonal distance. To calculate the lift, you need to measure how far the water in your fountain has to travel from the pump’s location in your fountain to the top of the fountain where the water comes out. Then you need to select a pump that lifts higher than that measurement. For example, if that distance is 24”, than you will need a fountain pump that lifts at least 36” high. The “maximum lift” is the maximum height that the pump will lift the water.

Selecting the Proper Pond Water Pump Tubing

It is also important to use the correct tubing size because it has a direct effect on the pond pump’s maximum lift capability. If you use smaller tubing than specified you will limit the pump’s maximum lift and the amount of water circulated.

Choosing the right pond water pump for your pond or fountain requires careful consideration and a little research upfront. Doing so will go a long way toward keeping your water clean and healthy and your pump operating efficiently.


How to Size a Fountain Pump

How to Choose a Pond Pump

How to Choose a Fountain, Waterfall or Pond Pump

The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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