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How to Choose the Correct Size Pond Water Pump

8/8/19
Revised: 12/6/21
Grainger Editorial Staff

Choosing a pump for your pond or fountain is an important step to maintaining proper water movement. Poor water circulation 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 non-submersible. 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 (GPH). They are easy to install and are sometime a more economical solution for smaller ponds (up to 1,000 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.

Non-submersible Pond Pumps

Non-submersible pond pumps are a reliable, energy-efficient option. They are installed in a dry location near your pond. Non-submersible pond water pumps are suitable for larger ponds (over 1,000 gallons). They are typically louder and more complicated to install than a submersible pump, but they also are easier to maintain.

How to Size a Fountain or Pond Pump

Pond pumps are sized by GPH at one foot of lift or height. Larger capacity pumps are rated by horsepower (HP). To find the size of pump you need, first calculate the volume of water in the pond. The equation is:

Pond length x pond width x pond average depth x 7.5 = volume in gallons

The length, width and depth should be represented in feet.

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 GPH at the height of the discharge. This is true if it also has a skimmer or waterfall.

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 1,000-gallon pond, then you need a pond pump rated at a minimum of 500 GPH.

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 represents 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 from the pond surface is called “maximum head.” Any horizontal/diagonal flow is then measured by its length and one foot is added to the maximum head per 10 feet 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 inches, then you will need a fountain pump that lifts at least 36 inches high. The “maximum lift” is the maximum height that the pump will lift the water.

Powering the Pump

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. Make sure you are using an outlet designed for outdoor use, with a ground fault circuit interrupter (GFCI) that will immediately shut off if there is an overload

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.

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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