There are several factors to consider when finding the right pool pump size for your swimming pool. These include the total volume, flow rate, total dynamic head, and filter size. Read on as I discuss each in detail and how it relates to your pump choice.
When shopping for a pool pump, it is really important to me to look into its size. I want to ensure that it is powerful enough to circulate pool water efficiently. If not, I will likely end up with a dirty pool. Having an undersized or oversize pool pump can also affect my electricity bill.
That is why I researched countless websites and pieces of expert advice. These allowed me to learn about the different factors affecting pool pump sizing and the best one for your needs.
So if you are also asking yourself, “what size pump do I need for my pool,” you have come to the right place. This article got you covered.
Continue reading as I answer this question for you!
What Factors Affect the Pool Pump Sizing?
When talking about the size of a pool pump, I usually refer to its maximum horsepower.
Pumps are available in different horsepower ratings. Smaller pumps with less than one HP are suitable for fountains and water features. Meanwhile, larger pumps ranging from one HP to three HP can handle residential inground and above-ground pools.
However, pool pump sizing is not entirely dependent on horsepower. In fact, it might be best to forget about going strictly by the maximum HP rating. That is because many factors come into play that might affect this feature. For instance, a one HP pool pump from a manufacturer may not circulate water as efficiently as another model with the same horsepower.
So, by now, you might be wondering about the considerations when sizing a pump. These include the following factors:
- The total volume of water in your pool (gallons)
- The flow rate necessary for an efficient pool filtration
- The total dynamic head, especially when your pump is located far away from your pool
- The right plumbing or filter size
I will further discuss each one in the next section. Keep reading!
How To Determine What Pool Pump Size You Need?
Below are the methods you need to follow to determine the best pump size for your swimming pool.
Calculate the Pool Volume
First, you need to determine how many gallons of water your swimming pool contains. You want a pump that is powerful enough to circulate the entire water in the pool.
You have to consider several pool dimensions to achieve an accurate measurement. These include the following:
- The shape of your pool
- The length and width of your pool
- The depth of your pool
- The average depth of your pool’s shallow and deep end, in case of variable depth pools
Calculating the total volume of a rectangular or square pool is easy. Use this formula:
length x width x depth x 7.5 = volume (in gallons)
The product of the length and width indicates the surface area of the swimming pool. Multiplying it by the depth results in the volume in cubic feet. The last figure in the formula refers to a cubic foot, which equals 7.5 gallons. The final product gives you the pool volume, which is expressed in gallons.
Meanwhile, pool owners with a circular pool must use a different formula for computing their total water volume. Arrive at the value by using:
3.14 x average depth x radius squared x 7.5 = volume (in gallons)
The radius in the equation is half of the diameter of the circular or oval pool. Measure the widest part of the pool and divide it by half to get the radius. You must also multiply it by itself, as the formula requires the radius to be squared. For instance, if you measured a six-foot radius, multiply it by 6 feet to get 36 square feet.
Finally, you can use two methods to get the capacity of an irregularly shaped pool. First, focus on the small, regular shapes in the swimming pool. Then, measure these different areas by using the formulas discussed above. Combine the volumes to find the total capacity.
Here is a simplified formula to help you:
0.45 x (A+B) x length x average depth x 7.5 = volume (in gallons)
Add together measurements A and B, multiply by 0.45, and the pool length results in the area of the irregular shape. You can easily calculate the rest of the equation as it is similar to the previous formulas.
If you do not want to bother with all these manual computations, you can use a pool volume calculator. You can usually find it on the manufacturer’s website or other online sites. Simply input the required figures to get the entire pool volume.
Determine the Pool Flow Rate
The next factor to consider when choosing the best pool pump size is the flow rate of your pool. It is easy to determine this element once you are already aware of how many gallons your pool has.
Use this formula to determine the pool’s flow rate:
Total pool volume (in gallons) ÷ turnover rate (in hours) ÷ 60 (minutes in an hour) = flow rate (in gallons per minute or GPM)
The turnover rate refers to the time it takes to move all the water through the pool filter. The ideal pool pump size must circulate the entire pool volume in less than eight hours or less. That allows you to turn the water over one to two times a day and ensure an effective filter system.
For instance, if you own a 24,000-gallon pool and prefer to turn the water every 8 hours, you will have the following formula:
24,000 (pool volume) ÷ 8 (turnover rate) ÷ 60 = 50
The minimum flow rate of the pump must be 50 gallons per minute (GPM).
Choose a pool pump close to this figure to guarantee efficient filtering and maintenance.
Consider the Total Dynamic Head (TDH)
Now that you know the pool’s flow rate, it is time to consider the total dynamic head. It determines the performance of the pump when turning over the swimming pool water.
The total dynamic head is the total equivalent height the pump needs to overcome in order to circulate water. It considers several factors that affect the amount of water pressure flowing in a system. These include the distance of the pump from your pool, the vertical rise of water, the size of plumbing pipes, and other pool equipment like filters and pool heaters.
After considering these elements, you will get the total dynamic head (TDH). It is the amount of resistance or pressure working against your pool pump as it draws water from the basin and drives it toward the pool.
While TDH is an essential factor in pool pump sizing, calculating the exact value is difficult. It might not be worth the effort.
We only recommend figuring out the exact TDH if your filter pump is far away from your pool or the water has to go a long way uphill to reach your swimming pool pump. If this is the case, it is best to hire a professional to determine the total dynamic head and the right pool pump size for your needs.
Otherwise, I usually opt to add a conservative figure for the TDH calculation. I use 15 meters TDH as the typical value for the average in ground swimming pool. Meanwhile, I add around 9 meters TDH for above-ground pool pump sizing.
Find the Right Filter Size
No matter what pump size you choose, you want to use the correct filter size for your pump. Ensure it has the right size to handle the filter’s flow rate.
Look for a filter flow rate with the same GPM or GPH rating as your pump. You can also consider a slightly larger filter size. Purchasing one means it can handle your pump’s power more efficiently. Other benefits of a correctly sized or slightly larger pump filter include the following:
- Longer filter cycles, or the time between backwashing
- Better water filtration
- Fewer chances for fine particles to go through the filter
- Faster cleanup of pool water
- Longer-running filter medium (cartridge, diatomaceous earth, or sand)
It is important to avoid a filter that is too small or too large in relation to your pump. Having a small filter size means a weaker water flow. Meanwhile, using a large filter size can put a strain on your pool equipment. After all, your piping can only handle so much movement or pressure, depending on their size. See below for the maximum flow rate of your pump based on your pipe size.
- 1.5-inch intake line = 42 GPM
- 2-inch intake line = 73 GPM
- 2.5-inch intake line = 120 GPM
- 3-inch intake line = 160 GPM
So even if you have a pump capable of filtering 100 gallons of water per minute, the 1.5-inch pipe will only move 42 gallons per minute (GPM) to prevent damage.
Frequently Asked Questions
What is the pool turnover rate?
When determining the ideal pool pump size, you might have come across the term “turnover rate.” It simply refers to how long your pump takes to circulate all the water through the filter.
For instance, if the pump circulates the water twice a day, it has a turnover rate of 12 hours. If it moves water four times daily, then the turnover rate is six hours.
You can determine the pool turnover rate by using the following formula:
Total pool capacity (in gallons) ÷ flow rate (in gallons per minute) = turnover rate (in minutes)
Here is the formula to get the turnover rate in hours:
Turnover rate (in minutes) ÷ 60 = turnover rate (in hours)
Can your pool pump be too big?
Many pool owners think that bigger is better. However, that is not always the case when it comes to pool pumps.
When buying a too-large pool pump for your needs, you risk putting stress on your plumbing pipes and filter. That means you might end up replacing them sooner than expected.
You will also get higher energy costs when using a pump that is too big for your needs.
Choose the right pool pump size if you want to avoid these problems.
What size pump do I need for my above-ground pool?
The best pump size for your above-ground pool will also depend on several factors, similar to an inground pool. These include the total pool gallonage, flow rate, total dynamic head, and plumbing or filter size.
However, you will likely need a small and less powerful pump for above-ground pools. That is because these types of pools are smaller than inground pools.
Check out our top picks for the best above ground pool pump.
Do pool pumps use a lot of electricity?
Pool pumps usually run several hours a day to circulate water and remove all kinds of debris. Hence, they can use a lot of energy. But how much electricity they actually consume can depend on various factors. These include the pump type and size, total pool gallonage, piping configuration, and filtration system, among other considerations.
You can start by checking the pump motor label to get an idea of its electricity consumption. You will find the volts and amps listed. If you encounter two figures, such as 115/230V, the motor can run on either 115 or 230 volts. You will also get variable Amps, such as 15.0/7.5. It means that the motor draws 15 Amps at 115V, and it draws 7.5A when running on 230V.
Now, you can multiply the volts by the amps to get the wattage. For instance, 115V times 7.5A is 863 watts.
Next, divide it by 1000 to arrive at the kilowatts (kW). In our example, 863 divided by 1000 is 0.863 kW.
Then, multiply the kilowatts by the number of hours you intend to run the pump. If you use it for 12 hours, multiply 12 by 0.863 kW to get 10.356 kilowatts per hour.
Finally, multiply the kWh per day by the energy cost per kilowatt in your area. For instance, the State of California has an average electric cost of $0.31/kWh. The product of 10.356 times 0.31 cents/kWh is 3.21. Thus, the pool pump can cost you $3.21 per day.
Conclusion
The right pool pump size can keep your water clear and ensure an efficient circulation system. The best way to get the ideal sizing is to determine the pool volume, water flow rate, total dynamic rate, and filter size.
I hope this article helped you choose the best size for your pool pump needs. When you’re ready to look at options, see our pick for the best pool pump.
