There is a tendency for people to just get the biggest pump that they can afford and be done with it. But the sad truth is, if a pump is bigger than what is required for your pool then you’re not only incurring heavier power consumption expenses but you’re also overpowering your filter system, making it wear out much faster than when the right pump is used.

On the other side of the coin, if the pump is too small, then your pool will become more prone to algae infestation as your pool water won’t be totally circulated and filtered. This will lead to the pool having dead spots or parts that the water stays stagnant and becomes a haven for algae, moss, and other pool baddies.

Hint: If the far edges of your pool is prone to algae infestation then this might be a sign that your pool pump is undersized.

Measuring your pool

Warning: This section contains some math calculations, if you don’t want to do the math then just note down the dimensions we’re looking for, contact us and we’ll do all of the math for you and recommend the perfect pool pump size for your pool!

The first step to determining the pool pump size needed for your pool is to know how much water there is in your pool. Prepare to get wet as this involves measuring the actual depth of the water in the pool.

For Square / Rectangular Pools

The basic formula for determining the water volume for square and rectangular pools is this:

Length x Width x Average Depth x 28.31 = Volume in Liters

To get the average depth of your pool, take the depth of the shallow end of your pool and add it to the depth of the deep end, and divide by two. Here’s a quick example. Let’s say the shallow end of your pool is 3 feet deep and the deep end is 7 feet deep. Add those two together 3 feet +7 feet =10 feet. Divide that by 2, what you’ll end up with is having an average depth of 5 feet.

For Example:

The pool is 30 feet long, 15 feet wide, and has an average depth of 5 feet.

The formula for that would look like:

(30 feet x 15 feet x 5 feet) x 28.31 Liters

So that’s 2,250 cubic feet x 28.31 Liters

So this particular pool’s volume would be 65,947.5 liters give or take a few. Take note of this number as this is important in determining the size of your pool pump.

For Circular Pools

The basic formula for determining the water volume for circular pools is this:

3.14 x radius squared x average depth x 28.31 = Volume in Liters

Did you get a headache yet? I just did and I was only typing that down. Here’s what the calculation calls for.

3.14 is pi, which is a mathematical constant. Don’t worry too much about this as this is constant everywhere in the universe.

To get the radius squared. You’ll need to get the radius first. The way to do it is to measure the distance at the broadest/widest part of the circular pool and divide it by two. So if at the widest point, your circular pool is 10 feet, then 10 feet divided by 2 is 5 feet. To square the radius, just multiply it by itself. So 5 feet x 5 feet = 25 is your radius squared. We already know how to get the average depth, so let’s just say as an example that the average depth is 5 feet.

Let’s plug that into the formula shall we?

(3.14 x Radius Squared x Average Depth) x 28.31

(3.14 x 25 feet x 5 feet) x 28.31 Liters

392.5 x 28.31 = 11,111.67 Liters

So this particular circular pool’s volume is 11,111 liters and we need to list that down to see which pump we need down the line.

For Kidney shaped and irregularly shaped pools

Depending on the actual shape of your pool, the calculations can be quite distressing. One good way to go about this is to divide your pool into rough rectangular and circular sections, calculate the volume for those sections and add them all together.

The formula for each irregularly shaped pool is as unique as the design of the pool itself, so if you need help on determining the volume of your irregularly shaped pools, give us a call or reach out via the contact us page and we’ll be happy to help you out.

I have the volume, now what? How do I determine which pump is for me?

Now that you have the volume, it’s just a matter of selecting the right pump with the right flow rate. The best way to explain that would be to do an example. Let’s use the first pool that we calculated the volume for.

Pool Volume = 65,947.5

Now, as a rule of thumb, we would want all of the pool water to be circulated within 6-8 hours, so lets use 6 hours as a baseline.

Divide the pool volume by the number of hours that you would want the pump to be running, so that would be 65,947.5 divided by 6.

This would give you 10,991 which means your pump should be able to turn around this much water in 6 hours. Since most pumps here in Australia are rated for Liters per minute, let’s divide that number by 60 to get how much water needs to be pumped per minute. So we have 10,991 divided by 60, which is 183.

To circulate all of the water in 6 hours, we would need to have a pump that’s rated at least 183 liters per minute. The closest pump we can get to hitting that mark is the Water TechniX Pump LEO 1.0hp. This pump can churn out 210 liters every minute. Remember, when choosing a pump, choose one that’s closest the required number of liters per minute, rounding up. This would give your pump enough extra power to compensate for dirt, filters, piping and other factors that will ultimately affect the flow rate of your pump.

Other Things to Consider

Aside from the volume of your pool water, there will be other concerns to worry about like heavy usage, environmental factors like leaves that may contaminate your pool, and other small things that may contribute to your pool water needing to get circulated more often. This is why we always recommend the Water TechniX Pump VorteX ECO Variable speed pool pumps. ECO pumps allow you to let the pump speed to energy saver to keep your pool clean during minimal use, and set it to full/regular mode in times when your pool water needs more circulation. A win-win situation. Not only will you get your pool water circulated at all times, but you’re saving money on electricity costs as well.
SEE ALSO: Cheapest and Most Affordable Way to Filter Your Pool Water


It’s always best to get the right sized pump for your pool for optimal water circulation and to be able to adapt to changing variables. I hope that I’ve provided you with enough of the basics to let you choose the right pool pump for your pool.  

Do you have any questions about this topic or the featured products? No worries, we're here to help! Drop us a question down below and we'll get back to you ASAP.

Happy swimming :)

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