How to Find the Right Size Pool Pump

When choosing a pool pump, knowing a little about the right size pump for your pool can save you a lot of time and money. Check out this step-by-step guide about how to find the correctly sized pump for your pool.

A pool pump is a crucial component of your filtration system. A common misconception when it comes to the horsepower on a pool pump is that the higher the horsepower, the better it is. This is definitely not the case. Having a properly sized pump helps avoid excess wear on your other pool equipment and also saves on electricity usage.

There are a few things to consider and evaluate before purchasing a pool pump. Keep in mind, every pool is different, so the proper research and calculation will lead you in the right path. Read along and we’ll cover everything you need to know before you make the plunge and purchase the right pool pump.

Types of Pool Pumps

As you may be aware, there are several types of pool pumps–mainly when it comes to speed: low, medium, and high. These speeds are important to consider because they regulate your pump usage and power consumption.

Single Speed Pumps

Single-speed pumps are considered the most popular type of pool pump. With a single-speed pump, the motor spins the impeller at only one speed according to the horsepower of the motor. Single-speed pumps tend to use a lot of power when they run for long periods of time and may not be the most ideal choice when looking for an energy-efficient option. Also, the state of California has prohibited the use of single-speed pumps for pool owners–mainly to help save on electricity usage.

Dual Speed Pumps

Dual-speed pumps have both a low and high option. When running at high, the dual-speed pump runs exactly like a single-speed pump. The difference is that there is a low-speed option that allows for more flexibility in usage. Dual-speed pumps are slightly more energy efficient than a single-speed pumps because you can set the pump to run on low during peak usage hours and when the pool is not being used.

Variable Speed Pumps

Considered the most energy-efficient pump, variable speed pumps also come with a higher price tag. The unique feature that variable speed pumps can boast about is that they come equipped with a permanent magnetic motor, PMM, which does not require electricity and can be digitally regulated to any speed. Variable speed pumps produce less friction, which means that this pump is energy efficient, quieter, and longer lasting.

Determine Your Desired Turnover Time

The first thing to determine is the desired turnover time, or in layman’s terms, how long it takes for the pool pump to cycle all of the swimming pool’s water completely. An ideal turnover time is 8-10 hours.

Use this formula to determine your turnover rate:

Pool Volume in Gallons ÷ Turnover Rate in Minutes = Flow Rate

For example: If a pool is 35,000 gallons and we want a turnover rate of 8 hours, our equation would look like this: 35,000 / 8 / 60 = 73 GPM (gallons per minute)

According to the table above, we need a pump with a 73 GPM rating in order to achieve an 8 hour turnover time. Even though we figured out how much water needs to be pumped, the water can only flow at the maximum rate if the plumbing is big enough to accommodate it.

Calculate the Maximum Flow Rate

The size of your pool’s pipes determines the maximum flow rate.

Count the number of intake lines for your pool and refer to the common pipe sizes below.

  • For each 1.5-inch intake line, the maximum flow rate is 42 GPM
  • For each 2-inch intake line, the maximum flow rate is 73 GPM
  • For each 2.5-inch intake line, the maximum flow rate is 120 GPM
  • For each 3-inch intake line, the maximum flow rate is 160 GPM

Size Your Pool Filter Accordingly

As our pool water makes it through the line to the pump, it is passed to another restricting element known as the pool filter. Every filter has a maximum flow rate as well, and if you go over that flow rate your water will not be filtered properly. We have included a chart so you can size your pool filter properly.

Sand Filters
Tank Diameter 19″ 21″ 24″ 30″ 36″
Surface Area 1.8 sq ft 2.3 sq ft 3.1 sq ft 4.9 sq ft 6.9 sq ft
Best Flow Rate 40 GPM 50 GPM 60 GPM 100 GPM 140 GPM
Cartridge Filters
Surface Area 100 sq ft 200 sq ft 300 sq ft 400 sq ft 500 sq ft
Max flow Rate 38 GPM 75 GPM 112 GPM 150 GPM 150 GPM
Best Flow Rate 30 GPM 50 GPM 75 GPM 100 GPM 125 GPM
D.E. Filters
Surface Area 24 sq ft 36 sq ft 48 sq ft 60 sq ft 72 sq ft
Max Flow Rate 48 GPM 72 GPM 96 GPM 120 GPM 144 GPM
Best Flow Rate 36 GPM 54 GPM 72 GPM 90 GPM 108 GPM


Narrowing down your pool pump choices according to your pool size, plumbing and filtration system is imperative if you want to purchase the perfect pool pump. Be sure to check out our wide selection of pool pumps and pool filters.

Happy swimming!