If you’ve wondered: “What is the right size for my pool pump?” you are not alone. That’s one of the most common questions in this industry.
Many people choose the biggest pump they find or just buy a model they can afford. However, the outcome is not usually favourable in either case.
Choosing the right size for a pool pump is important for many reasons. Here, you’ll understand why. In addition, you’ll be able to find all the information you need to make the right choice.
Understanding Pool Pump Sizing
The pump is one of the biggest purchases you can make for your pool. Also, it’s the heart of its circulation system. Therefore, you must make sure you pick the right one.
Why Is Proper Pump Sizing Important?
As mentioned, this piece of equipment functions as the main part of the pool’s circulation system. Its main objective is to circulate water through the filter to remove debris, hair, body oils, dirt, and other unwanted elements.
After this process, the pump distributes chlorine produced by the system’s chlorinator throughout the entire pool, keeping the water sanitised and clear.
However, when you don’t have the right pool pump size, there’s a high risk of having dirty and contaminated water. Additionally, it can affect all pool equipment.
If your pump is bigger than required for your swimming pool, you’ll be overpowering the filter system. As a result, it’ll wear out or break faster.
Also, using the wrong pool pump size means you may incur more power consumption expenses.
On the flip side, when the pool pump is too small, the pool water won’t be properly filtered and circulated, so it’ll be more susceptible to algae infestation.
Consequently, your swimming pool will have dead spots and stagnant water, promoting the growth of moss, algae, and other undesirable organisms.
Factors that Affect Pool Pump Sizing
There’s a huge range of pumps out there. You can find multiple sizes, features, and models. However, as mentioned, choosing the right one is critical to ensuring your pool equipment’s proper functioning and maintaining water safety.
In addition, it often requires planning and measuring, as you need to consider different aspects to choose the best pool pumps. These are:
- The pool volume or number of litres of water in your pool
- The Total Dynamic Head
- The flow rate
If you don’t have that information, don’t worry! Here’s everything you need to know on how to size pool pump equipment.
How to Calculate Pool Volume
Do you want to calculate the volume of your rectangular or square pool? You only have to use this simple formula:
- Length x Width x Average Depth x 28.31 = Pool volume in litres
Check this example: Your pool is 30 feet long, 20 feet wide, and 5 feet deep. In this case, the formula would be:
- (30 feet x 20 feet x 5 feet) x 28.31 litres, which translates to 3,000 cubic feet x 28.31 litres
In other words, your pool has a volume of 84,930 litres.
However, if your pool is circular, you must use another formula:
- 3.14 x Radius Squared x Average Depth x 28.31 = Pool volume in litres
How to Calculate Flow Rate Requirements
Besides the pool volume, you also need the flow rate. Essentially, it’s how many litres the pump moves per minute (lpm).
If you want to calculate the flow rate, you need the pool volume and turnover time, which is how long it takes for the water volume to pass through the circulation system.
Based on the industry’s estimates, the typical turnover is four hours for indoor pools and six hours for outdoor pools.
Check this example: Let’s say you have an outdoor 85,000-litre pool. Also, your pump has a six-hour turnover time. This is the best way to calculate the flow rate:
- Turnover time in minutes: 6 hours x 60 minutes: 360 minutes
- Flow rate: Divide the pool volume, which is 85,000 in this case, by the turnover time in minutes
- Result: Around 236 litres per minute
How to Calculate the Total Dynamic Head
Once you have the flow rate, it’s time to calculate the TDH or Total Dynamic Head in metres. It’s a metric that calculates the pump’s resistance to the water flow or the “total pressure” when the water is flowing.
Overall, most inground pools are around 15 metres TDH, but above-ground pools typically fall somewhere around 9 metres TDH. However, you need to consider three different factors to calculate it:
- Pipe head loss
- Fitting head loss
- Elevation head loss
This is the formula to consider:
- Pipe Head Loss + Fittings Head Loss + Elevation Head Loss = Total Dynamic Head
What Should You Do Next?
After calculating these numbers, you just have to use a pool pump size calculator or check out the different brands and models available to pick the right one.
How to Use a Pump Performance Curve
Are you still wondering: “What size pump do I need?” There’s still a lot of maths to do! However, you can use a pump performance curve chart to see if the model you chose will perform well for a specific application.
With a pump performance curve chart, you can consider different metrics, including the following:
- Water pressure
- Impeller trim
- Net Positive Suction Head Required (NPSHr)
Tips for Properly Sizing a Pool Pump
Do you still need help choosing the right pump? Consider these tips:
Determine the Horsepower Requirements
Horsepower, or “hp,” measures the motor’s or engine’s power or output.
In this regard, this measurement tells us how strong and effective a pool pump is.
Why is it important? Well, the greater the horsepower, the greater the water volume this device pumps.
Know the Types of Pool Pumps and Their Sizes
There are three types of pool pumps, which are the following:
This is the original style of a pool pump and is usually the cheapest. In terms of speed, these devices operate at 3450 RPM. However, it is not adjustable.
A dual-speed pool pump has both high and low-speed settings. Also, these devices are more efficient than single-speed models. However, they’re more expensive.
Finally, there’s the variable speed pump, which is a great option for those looking for quieter devices with maximum efficiency, as they have a full range of speeds and allow you to adjust the flow rate.
Choosing the Right Impeller Size
In addition, you must choose the right impeller for your pool pump since this part (it’s connected at the end of the motor’s shaft) propels water at high speeds.
The impeller is considered the most important part of the pump.
Compatibility with Pool Filters and Other Equipment
If you want to choose the right pump, you should also consider the pool filter and other equipment. As mentioned, the pump can directly affect other tools’ functioning.
After calculating the flow rate and the TDH, you can pick the right size for your pool pump. Based on its input, you should also pick the right filter to go with it. Check the below examples:
- A 500 W pool pump is compatible with a 20″ filter
- 750 and 1100 W pumps are compatible with 25″ and 28″ filters
- 1100 and 1800 W pumps are compatible with 28″ filters
- 1800 and 2000 W pumps are compatible with 33″ filters
Cost Considerations and Pool Pump Sizing
Besides measurements to ensure efficiency and top-quality performance, you must also consider costs. As mentioned, prices vary depending on the type.
Variable-speed pool pumps tend to be more expensive. Additionally, costs may vary based on size. The more powerful the pool pumps are, the more expensive they’ll be.
Noise Level and Pool Pump Sizing
Pool pumps also produced noise. Single-speed models tend to be noisier. However, if you want a quieter device, you can choose a variable-speed pump.
Considering the noise level can also help you save money, as you’ll be able to use a quieter device during off-peak hours when electricity is less expensive.
Maintenance Requirements and Pool Pump Sizing
Finally, there are maintenance requirements. You must make sure you clean the pump and the impeller. In addition, the device must have proper ventilation and a cover.
In terms of cleaning, the process is similar for all sizes. However, larger pumps may have more parts or require more cleaning time.
As you can see, calculating the right size for your pump isn’t rocket science. However, it involves doing some maths. Moreover, you must consider multiple aspects to make a wise choice.
Fortunately, you only have to spend a few minutes to get the information you need and use a pool pump size calculator to speed up the process.