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What Size Pump Do I Need for My Pool?


Whether you’re buying a pump for the first time or looking for a replacement, it’s important to carefully evaluate your pool needs. This is mainly because today’s pumps are much more efficient and if you simply go by horsepower ratings, chances are you’ll oversize your pump. So, what size pump do I need for my pool? Some things to consider are your pool size and depth.

In this article, we’ll discuss how to choose the right sized pump for your pool. We’ll point out everything from finding how many gallons in your pool, the piping to your pool and determining the minimum and maximum flow rates.

Determine the Minimum Flow Rate

Determine the Minimum Flow Rate

The minimum flow rate, also referred to as the turnover time, refers to the flow rate that must be maintained to circulate all the water in the pool through the filter within a certain number of hours. An average home pool should have a turnover time of about eight to ten hours. If your pool is used heavily, aim for a shorter turnover rate. Once you have determined a turnover rate, you will need to determine the number of gallons your pool holds (there are plenty of pool gallon calculators you can use). You can then calculate the precise needs of your pool using the following steps:

For example; let’s assume that you have 24,000 gallons of water in your pool that all needs to be cleaned within 8 hours. Divide the amount of water in your pool (in gallons) (from the step above) by eight. So, if your pool has 24,000 gallons of water, the equation will look as follows:

24,000 ÷ 8 = 3,000

Since pumps are categorized by the gallons, they move every minute, you’ll need to divide the number above by 60. Determining the gallons per minute:

24,000 gallons ÷ 8 = 3,000 ÷ 60 = 50 GPM (gallons per minute)

Check the Plumbing Flow Rate

You’ll want to check the pool system plumbing next. Count the intake lines (suction lines) as that will determine what the maximum flow into the pump will be. Generally, the velocity of the water through the piping shouldn’t exceed 7 feet per second. It’s also important to make sure the lines going back into the pool (return lines) will support the same level of flow.

Determine the Maximum Flow Rate

The flow rate of any given pool system is limited by the equipment and the size of the piping. This determines the maximum rate of flow through the system. Even if your pump can move 80 GPM, that won’t make much of a difference if the piping only allows 50 GPM through it. An over-sized pump will actually damage the piping as it will strain against the piping and could cause a pool leak.

One Step Closer to Being a Pool Expert

One Step Closer to Being a Pool Expert

By following the steps mentioned above, you can now answer the question: what size pump do I need for my pool. Once you figure out how many gallons your pool has, then you will be able to calculate the GPM for the filter. Then shortly after be able to calculate the maximum flow rate for the piping system to be able to find the right size pump for your pool.