A swimming pool pump is a vital component of your backyard pool, circulating water through the filtration system, mixing chemicals, and sanitising the water to eliminate any nasties.
But buying or upgrading your pool pump can be a tricky thing when you start shopping online. There’s the pool pump jargon to wrap your head around, not to mention the complex sums you need to do to calculate the appropriate pump size for your pool.
But understanding these complexities is important: purchasing the wrong pump for your pool can mean much greater problems down the line.
There are four things you’ll want to consider before buying your pump:
But it’s not as simple as that. While you may want to start with a cheaper pump option, you may find your costs escalating over time, since the cheaper pumps aren’t always the most energy efficient.
Different Pump Features
The first thing you’ll notice in your research about pool pumps is that their power is commonly measured by horsepower (hp). The greater the horsepower, the greater the volume of water the pump can move.
You have plenty of choice when it comes to your pump’s performance, varying from as little as .75hp to as much as 2.5hp. But you have to be careful in your choice; a pump too large can do damage to your pool just as a pump too small can be completely ineffective. See below to find out how to calculate the right size for your pump.
A general rule is that the larger and deeper your pool is, the more powerful the pump will need to be to move the water about effectively. This is normally measured as litres per minute or L/min.
The pool pump can use up to 70% of your pool’s total energy consumption, which means it pays off to factor energy efficiency into your purchasing decision.
A multi-speed or variable-speed pump, though slightly more expensive, is generally more energy efficient since it is able to adjust its speed for various jobs. Some even come with automatic controllers which switch the pump’s speed between tasks.
For example, variable-speed pumps (such as the E3 variable speed pump) can use a higher speed during heavy pool vacuuming, but adjust to a lower speed during the regular filtration cycle. Fixed speed pumps on the other have work at the same capacity regardless of the job – and thus can consume much more energy.
If you want to your pool pump to last a decent distance, look out for a device with non-corrosive metal internal parts. The body should have thick, protective walls made from a plastic such as the Noryl Plastic used in the car industry.
Picking the right pump
Now you understand the speed and power variations in the pump, it’s time to learn how to calculate which pool pump is best for your pool. Don’t worry: a calculator can do most of the work for you.
The calculations you’ll make for your pump typically determine how much water your pump will need to move per hour (called the flow rate). You’ll need to know your pool’s capacity, turnover, maximum flow rate, and resistance.
It’s important you get your calculations right; an inadequate pump can lead to damaged filters and cloudy water.
If your pool is a new installation, luck would have it you should know its volume. Otherwise, you may have to calculate it.
First you have to determine your pool’s surface area. If you have a rectangular pool, it’s easy: simply multiply its length by its width. With an irregularly-shaped pool, you may need more help (don’t worry, that’s what we’re here for – see below).
Next you’ll need to figure out your pool’s depth, which is easy if the pool floor is level. If it isn’t, add together the maximum and minimum depths and divide by two to reach the average depth.
Finally, you’ll reach your pool volume figure by multiplying your average surface area with its average depth. Times that by 1,000 and you’ll have your volume in litres.
You need to know your turnover measurements to find out the best flow rate for your pool. The turnover rate measures the minimum time it takes to cycle all your pool water through the filter. This is typically 6-12 hours.
To find out the best flow rate for your pool, you’ll have to divide your pool’s volume by the turnover rate in minutes.
So for example, if your pool volume is 60,000 litres and your turnover rate is 7 hours (or 420 minutes), you want a pool pump that can turn over about 140 litres per minute. This isn’t much, so a pump with 0.75hp is best for this job.
It’s always best to choose a smallest pool pump size for your pool so you don’t risk the potential damage a larger pump can cause.
Once you’ve figured out your flow rate, you need to finally calculate the water resistance in your pool. This resistance is ‘friction loss’ created as the water passes through the pool’s circulation system.
You will need to add up the sum of all your various pool equipment’s friction loss. Every bit of pool equipment creates resistance to water flow, including pipes, filters, heater and pools cleaners. Not just that, the size, lengths, and types of equipment can affect your total amount of resistance (called, confusingly we admit, ‘feet of head’).
It’s quite simple: the greater your feet of head, the stronger the pump you need.
Charts should come with all your equipment detailing how much resistance it provides. You should then be able to tally up the total to come to your total amount of resistance.
If this isn’t the case, using a pressure metre you can gauge the pressure of water flowing into the tank and multiply it by 2.31.
Next gauge a vacuum reading on the pump suction line. Times that by 1.13.
Add the two numbers together. The final number is measured as feet of head.
Pump manufacturers supply performance charts that help you determine which model and horsepower is best for your pool.
Ready to Buy?
We admit this is a lot to take in and can be difficult to deal with on your own. But as we’ve already said, that’s why we’re here.
Call us today on 1300 679 885 if you need any additional help or services. Or if you’ve already done the maths and know exactly what you need, check out our full range of pool pumps.
At the AOL Pool Shop, we have swimming pool experts who can help you out with all your needs. We can help calculate the sums, choose the right pump and even install it for you. Find out more about our professional pool service here.