Choosing a new pump for your in-ground or above-ground pool can be daunting. There are many options to choose from. In this step-by-step guide, we show you how to choose the best and right size pump for your pool.
We’ll start with some general pump recommendations, then get into the steps to choose your pool pump.
- Top Pool Pumps For Pools
- How To Choose the Right Size Pump
- 1. Work Out the Pool’s Volume
- 2. Calculate Ideal Pump Flow Rate
- 3. Check Pool Filter Min/Max Flow Rates
- 4. Measure the Pipe Diameter
- 5. Add in Total Dynamic Head
- 6. Choose the Type of Pump
- 7. Choose the Pump Size
- Average Pool Pump Flow Rates
- Measure Flow Rate with a Flowmeter
- Can a Pool Pump Be Too Big?
- Final Thoughts
A correctly sized pool pump will turn over all the pool’s water at least once in 8 to 10 hours. The pump’s flow rate should be between the minimum flow and maximum flow rate of the filter. The right size pump will also match the pool’s pipe size with 1.5″ pipes requiring a flow less than 44 gallons per minute (GPM) and 2.5″ less than 120 GPM.
Top Pool Pumps For Pools
For a more specific recommendation, let’s group this list according to pool pump sizes:
Best Pool Pump for Pool (10,000 – 15000 Gallons)
10,000 – 15,000 gallon pools need a pool pump with flow rate between 20 and 35 GPM.
Based on our flow rate per pump size(in hp) table above, a 1hp pool pump will generate this flow rate.
Here are top choices for pools 10,000-15,000 gal in capacity:
This product from Intex pools is designed to generate a flow rate of 1600 Gallons per hour (27 GPM).
It also has a 6-functional control that allows the user to switch the pump settings between filter, backwash, recirculate, rinse, drain, and close system function.
Best Pool Pump For Pool (20,000 – 40,000 Gallons)
20,000 – 40,000 gallon pools require a flow rate between 40 GPM and 82 GPM.
Based on our flow rate per pump size (in hp) table above, a 1 or 1.5 hp pool pump should generate this flow rate.
Here is a top choice based on this specification:
This product by Hayward is a 1.5hp pool pump designed to pump up to 90 GPM in most pools.
It requires less maintenance and is highly efficient.
Best Pool Pump For Pool (40,000 Gallons and above)
Pools that contain 40,000 gallons of water and above are usually large. Such pools require a flow rate between 83 GPM and 120 GPM.
Based on our flow rate per pump size (in hp) table above, a 1.5 or 2 hp pool pump should generate this flow rate.
Here is a top choice based on this specification:
This pool pump from black+decker is designed with a low speed option for effective filtration.
The pool pump is user-friendly due to an easy to use touch pad for speed settings and high performance.
How To Choose the Right Size Pump
Here’s a step-by-step guide for choosing a pool pump for your inground or above-ground pool. This guide is also suitable for Intex, Summer Waves and Bestway pools.
What is Turnover?
In clearer terms, turnover time refers to the period of time it takes your pool pump to move all the water in the pool through the filter.
In general, you want to turn the water over about 1-2 times a day for effective filtering. This cycle of pool water circulation is known as “turnover.” And in an ideal world, you’d leave the pool pump running 24/7 but that’s not practical for most as the running costs would be too much.
What is Pool Flow Rate?
The flow rate of a pool is the speed at which the water is being circulated through the pool’s circulation system at a given time. Pool flow rate meters usually display the flow rate in gallons per minute (GPM) or liters per minute (LPM).
The ideal flow rate for small pools is between 40 GPM and 60 GPM.
Bigger pools will require a flow rate between 80 GPM and 100 GPM.
These flow rates will depend on your plumbing and also the size of your equipment (pump size, heaters, filter sizes, water features etc.).
A 0.5 to 1hp pool pump will do this in most residential pools.
If you’d like to know what your pool flow rate is without the math, check out our article:
Do You Need a Pool Flow Meter? (and how to install)
But let’s not guess. Here’s how to choose a pool pump, step by step:
1. Work Out the Pool’s Volume
First, you’ll need to know how many gallons of water the pool can hold. Basically, you want to multiply the width and length by average depth. You can use this pool gallon calculator here to figure that out.
For this guide, let’s go with a 32,000 gallon pool.
2. Calculate Ideal Pump Flow Rate
Calculate how many gallons of water the pump needs to circulate per hour to complete the one turnover in 8 hours. That is all the water has flowed through the filter.
To do this, divide the volume of the pool (in gallons) by 8 (hours).
For this guide, our swimming pool contains 32,000 gallons. That’s 32000/8 = 4000 gallons.
This means the pool pump has to pump 4,000 gallons of water per hour to complete the turnover of a 32,000 gallon pool in 8 hours. But pumps are usually rated in gallons per minute.
Convert to Gallons Per Minute
Pool pumps are usually labeled by the number of gallons they can pump per minute. The next step is to divide the required gallons per hour (4000) by 60 (minutes in an hour) to get the gallons per minute.
That’s 4000/60 = 66.7 (approximately 67 Gallons per minute).
So for a 32,000 gallon pool, you need a pool pump with flow rate between 53 GPM and 67 GPM.
If you wanted to turn the water over in 10 hours, simply substitute 8 in the calculation above for 10. So you’ll get 32000/10 = 3,200 Gallons per hour required. Then 3200/60 = 53 gallons per minute.
Using the flow rate of the pump rather than the horsepower rating is how we’re going to choose our pump. The goal is to complete your pool turnover with a pool pump that will use the least power or energy, in other words, the least horsepower.
So you see, you really don’t need a bigger pump for your pool unless you just want a higher electricity bill.
3. Check Pool Filter Min/Max Flow Rates
For pools, the maximum flow rate of the pump has to be equal or less than the maximum flow rate of the filter. It must also be greater than the minimum flow requirements.
If the pump’s flow rate is greater than the filter maximum ratings, pool filters do not work well. This is because the pump’s flow rate will be greater than the filter media rate. The Filter Media Rate (FMR) refers to the volume of water that the filter pleats or sand can handle.
The increased flow rate will force debris deep into and sometimes, through the pool filters and back inside the pool.
Eventually, it will result in poor water filtering and cleaning. You’ll also have a reduced lifespan of the filter media, whether that’s a cartridge, sand, or diatomaceous earth (DE).
If the pump’s flow rate is too low, this will lengthen the time it takes to turn over the pool’s water. And in addition to this, the filter will not perform backwashing properly.
You may have to do some searching for this information. Grab the model number, which is hopefully written on the side of the filter, Google it and search for the filter’s specifications. They will have min and max flow rates.
Make a note of these numbers.
4. Measure the Pipe Diameter
It’s important to note that your pool pump size choice is also affected by the sizes of the pool’s pipes and by the other factors mentioned above. Your pump size needs to be less than the maximum flow rate of the pipes.
Grab a tape measure or better yet, a set of calipers and measure the diameter of the pipe coming out of your pump or filter. Take a note of this.
To fully understand the importance of the pipe size, here is a table of the maximum flow rate allowed according to pool pipe sizes.
|Pool Pipe Size (in inches)||Pool Pipe Type||Maximum Flow Rate Allowed|
Most pools are designed with a pool pipe size between 1.5 and 2.5 inches. This means a pipe-allowed flow rate between 44 GPM and 120 GPM.
If the pipe size only allows 60 GPM, then using a larger 100 GPM pool pump will not give you 100 GPM of water circulation in your pool.
Using a pump that is too large for the pipes will cause the pump to be starved of water. When this happens, the pump will cavitate and not operate correctly.
5. Add in Total Dynamic Head
So far we’ve covered the ideal flow rate your pool needs and the limits of the pipes and filter. There are several other factors we need to take into account that can impede the flow of water.
Factors such as:
- distance of the pump from the pool
- the number of corners or bends in the pipes
- height difference i.e. a pump may be installed higher or lower than the level of the pool
- the size of pipes
- other equipment installed such as heaters and water features
All of these factors create friction losses, which means the pump will use more energy to make the water flow. In fluid dynamics, this is what’s known as Total Dynamic Head.
It’s not easy for the DIYer to calculate the impact of these things without a working knowledge of fluid engineering.
What should you do then?
Here’s a table showing an average of the total dynamic head for residential pools.
If your pool is a fairly standard pool and your pump is not 50 feet away or located well below or above the water level of your pool, use these measurements. Otherwise, you may need a larger pump and a professional to help you choose the right size pump.
6. Choose the Type of Pump
Single-Speed Pool Pump
Of all pool pumps, the single-speed pool pump uses the most power. The pool pump when on, runs at top speed at about 3500 RPM. It can’t be tuned to run efficiently since it only runs at one speed.
In some states (California), it’s not legal to install single speed pumps.
Unlike single-speed pool pumps, the dual-speed pool pump has speed settings that allow the user to alternate between running the pump at a low and high speed.
The idea of these pumps was that they are supposed to save money using two speeds.
But the problem is the pump is not very effective in cleaning pool water when switched to low speed. At a low setting (about 1750 RPM), the pool pump will struggle to complete the water turnover in the ideal 8 hours, especially in larger pools.
At high settings, the dual-speed pool pump can reach top speed at about 3500 RPM. This speed is enough to clean most pools.
The math usually doesn’t work out when calculating the water turnover and costs to run the pump.
Variable Speed Pump
This is the best of the lot and the way of the future. The variable speed pump has a wide array of pump speeds (in RPM) to pick from.
Most variable speed pool pumps allow the user to switch between pump speed of 450 RPM and 3500 Rpm. The advantage of this is that it can be tuned to get the right amount of flow for your pool whilst maintaining maximum efficiency. There is a speed for every task ranging from refilling to draining the pool.
They generally save up to 70% on running costs compared to a single-speed pump and are also far quieter. Every pool should have one of these.
7. Choose the Pump Size
Now you know how much water your pump needs to move, the minimum and maximum flow rate of your filter, the maximum flow rate of your pipes and have the total dynamic head, you can choose your pump size.
There are a number of specifications to choose a pool pump and they can be confusing at first.
- Type of pump
- Flow rate (measured in gallons per minute)
- Inground or Above-ground pump
Choose Your Type of pump
We talked about this above and you should by now know if you want a single speed, dual speed or variable speed.
Choose the Voltage
Pool pumps run on two voltages: 115V, 230V or both.
Check which voltage your existing pump runs on. It’s usually written on the side of the pump. Or if you’re unsure, consult an electrician.
Inground or Above-ground Pump
There are two types of pumps. Pumps designed for above-ground pools and pumps designed for inground pools.
Pumps suitable for above-ground pools are not self-priming and need to be installed below the water level. They are also less powerful. Inground pool pumps are self-priming and can be installed above the water level of the pool. They tend to be more powerful.
Make sure you choose a pump that suits your pool.
What is Horsepower?
Horsepower (hp) is a measurement of a motor or engine’s power or output. So a 2hp pool pump is stronger and more effective than a 1hp pool pump, well in theory that is.
This is because horsepower ratings can be deceptive. A 1 1/2 hp full rated pool pump could be the same as a 2 hp uprated pump. The other thing is, the same pump will have a different flow rate in different pools.
This is because of the total dynamic head factors we talked about early like length of pipes, diameter of pipes and the other pool equipment.
Where to Find Pool Pump Flow Rate
We’re going to ignore horsepower and choose a pump using the pump’s performance graph. After all, what the pool needs is not increased horsepower, but an increased flow rate.
Each manufacturer will publish a graph like this one below. The colored lines represent a model of pump and their respective performance. That is their flow in gallons per minute with different amounts of total dynamic head.
Here’s how to read a pool pump’s performance graph.
To work out the correct size pump, you need the idea flow rate, we worked this out earlier, and the total dynamic head (TDH). Remember for average inground pools use a TDH of 50-60 and for above-ground pools, use a TDH of 20-30.
Let’s assume your TDH is 50, simply look at the axis (vertical in this case) that has TDH, find 50 and slide horizontally across the graph until you hit one of the pump lines (green or blue/purple line above).
Now, follow this vertically down and look at the flow on the horizontal axis. If the flow is about what you need, then the pump is suitable. It’s ok for it to be a little larger or smaller but not too much. Find the pump closest to what you need.
In this example, if we needed a flow rate of 65GPM, using a TDH of 50, slide across the graph horizontally and check both of the colored lines. The green line pump only has a flow rate of about 46GPM so it’s too small. The purple/blue line has a flow rate of approx 70GPM – perfect.
Average Pool Pump Flow Rates
And if that is all too much for you, let’s compare some average flow rates of different pumps to get an idea of which pump size you’ll need for your pool. These aren’t 100% accurate because it depends on total dynamic head, but it will give you an idea.
A table of pool pump sizes in hp and the expected minimum flow rates:
|Pool Pump Size (in hp)||Expected Flow Rate (in GPM)|
Measure Flow Rate with a Flowmeter
If you already have an existing pool pump, you can shortcut this by installing a flow meter. A flow meter will measure the current water flow. All you then need to do is measure the pool’s volume and determine if the flow rate is high enough. If it is, install a similar-sized pump.
Remember, you want the flow rate to be enough to pump all of the pool’s water through the filter in 6-8 hours. A flow meter will give the measurement in gallons per minute, simply multiply by 60 to work out how long it will take to turn over all of the pool’s water.
Here’s some recommended flow meters:
We have a full article on flow meters here:
Do You Need a Pool Flow Meter? (and how to install)
Can a Pool Pump Be Too Big?
A pool pump can certainly be too large. Many pool owners in fact fall for the usual way of thinking that bigger is better. This isn’t true when it comes to pool pumps. A pump should only be as big as it needs to be.
A pump that is too big will:
- Use more electricity
- Not filter the water properly
- Add additional strain on the pool’s plumbing
We have a full article explaining what happens if you use a pool pump that is too large for your pool: Can I Use a Bigger Swimming Pool Pump?
Choosing a pool pump need not be difficult. To work out the ideal pump for your needs, first, calculate the volume of the pool and then the time it will take to turn over the water in less than 8 hours.
Next decide if you want a single speed, dual speed, or the most efficient pump of all, a variable speed. Once you have this decided, now you can check out the various model of pumps. Look at the flow rates and voltages to see if they meet your needs.