What size pool filter do I need?

Follow these simple steps to calculate the size pool filter you need to keep the water clean and looking great all year long.

Step One

To calculate litres per minute, start by finding the surface area of your pool and the volume of water your pool can hold. You should be able to find out the surface area of a new pool by contacting the vendor that you purchased it from but if you’re calculating it yourself it’s fairly straightforward.

For a rectangular pool you’ll need to multiply the length by the width and for a circular pool, take the radius of the circle, raising it to the power of two, then multiplying the product by 3.14.

Step Two

You then need to find the pool’s maximum volume of water so as to establish how much water can move through the filter in about a minute. This is referred to as the “flow rate”. To find your pool’s volume, take the maximum volume of water your pool can hold (again for new pools this amount can be requested for by the vendor) and divide it by 360. This will tell you how many litres of water goes through your filter in a minute.

Tip: For maximum efficiency, opt for a pool filter that is slightly bigger than necessary.

Step Three

The next step involves figuring out your pool’s turnover rate, this is, knowing how long it will take for the water to cycle through the filter entirely. Most health codes require a minimum filtration turnover rate of two complete turnovers of the water in a 24-hour period and a turnover rate of 8 or 10 hours is the typical sizing rate for pools today.

By taking your pool’s volume and turnover rate, you can select the most suitable pool filter.

Find out more pool tips by visiting the pool section of our Learning Library.

Feature image: Garden and pool by Clare Cousins Architects in collaboration with Eckersley Garden Architecture