How Long To Run Pool Filter

Your own personal pool is the absolute dream. There’s nothing like waking up on a sunny Saturday morning and taking a dip before breakfast.

But as enjoyable as pools are, they require a fair bit of maintenance, one of the main aspects of which is filtration.

How Long To Run Pool Filter

If you don’t filter your pool water for long enough, you risk coming out of that early morning swim looking less glistening and invigorated, and more like a swamp monster.

Don’t worry, though, friend. I’m not going to let that happen to you. In this article, I’m going to give you the lowdown on pool filters and how long you need to run them each day.

How Long To Run Pool Filter - Turnover

In an ideal world without energy bills and a planet in the throes of an environmental crisis, we’d keep our pool filters running 24/7.

The more we filter the water, the cleaner it is, but unless your name is Elon Musk, Bill Gates, or Jeff Bezos, it’s not a realistic option.

Instead, we have to settle for one complete turnover a day. What is a “turnover”, you say? Well, in this context, one turnover is a complete cycle of your entire pool’s water content.

That’s right, folks. One cycle is enough to keep your pool clear as the glimmering Caribbean Sea. The reasons we should keep it to one turnover a day are four-fold:

  • Saves on scary energy bills.
  • Good for the environment.
  • Doesn’t leave any water to stagnate.
  • Prevents premature wear of pool equipment.

How Long To Run A Pool Filter - Turnover Rate

So, we’ve established that we should run our pool filters long enough to cycle all the water in our pool once over per day — great! But that still doesn’t give us an exact time limit.

To put a figure on our filter’s runtime, we need to work out something called turnover rate.

How Long To Run Pool Filter

The turnover rate is the time it takes for our filtration systems to cycle through the entire contents of the pool once — simple, right? Well, kind of, but here’s the thing.

Even though the average turnover cycle takes roughly 8 hours, as pools come in a bunch of different shapes and sizes, I can’t give you a definite answer. I’m afraid we’re going to have to use...math.

Boo, I know, but if we want to keep that pool a pool and not a pond, we just have to bite the bullet, break out the calculators and get to work.

How To Calculate Turnover Rate - Flow Rate And Volume

Unfortunately, to calculate the turnover rate of our pool, we first have to introduce another confusing phrase, flow rate.

Flow rate refers to how much pool water a filter can process in an hour, and it’s usually expressed as (number)m3/hour.

Every filtration system will have a different flow rate, so to figure yours out, you’ll need to take a reading from a pool flow meter. But let’s put a pin in flow rate for the time being while we focus up on volume. 

Pool volume is the second part of the equation we need to calculate the turnover rate of our pools. Don’t worry if you’re not sure what your pool’s volume is, because I’m going to show you how to work it out.

If you have a traditional rectangular pool, the sum is…

  • Length x Width x Depth = Total Volume in m3

...but if you have a variable depth, i.e. a shallow end and a deep end, you’ll need to figure out the average depth in order to complete this sum. Luckily for us, it’s not as hard as it sounds.

All you have to do is measure the shallowest shallows of the shallow end and the deepest depths of the deep end, add the measurements together, then divide by 2. Or, put more succinctly…

  • S + D ÷ 2 = Average Pool Depth

Now for circular pools. Things get a little crazy here, as we have to use Pi. Remember that little doorway-lookin’ symbol that made geometry in school, hell? Yeah, that thing. The circular sum is as follows…

  • ???? x Radius2 x Average Depth = Total Volume in m3

Phew...that’s the hard part over with, but don’t set that calculator aside just yet. Next on the agenda is combining our flow rate with the total volume of the pool in the following sum…

  • Pool Volume ÷ Flow Rate = Turnover Rate

...For instance, let’s say your pool has a total volume of 80m3, and your filter’s flow rate is 20m3/hour, we would do 80 ÷ 20, which equals 4, meaning your turnover rate is 4 hours, so you’d have to run your pool filter 4 hours a day to cycle the water once.

When Should I Filter My Pool?

If you want to save yourself a few bucks on the old energy bill, it’s a good idea to contact your energy supplier and ask them what times of day are considered off-peak.

These will usually be early in the morning and later in the evening.

You don’t necessarily have to run your filter for the entire turnover in one session. Feel free to split it up over the two off-peak portions of the day.

I’d also recommend investing in a pool cleaning net, so you can deal with the larger debris yourself and take the pressure off your filtration system.

Summing Up

We’ve gone down a bit of a rabbit hole with these calculations today, so let’s take another quick look at what’s been covered.

  • You need to cycle the entire contents of your pool once a day.
  • This is known as a turnover.
  • How long it takes is known as the turnover rate.
  • To find the turnover rate, you need to know the flow rate and volume of your pool.
  • Divide the volume of your pool by the flow rate, and voila; that’s your turnover rate.

Simply turn on that filter of yours for the full turnover rate once a day, and you’ll keep the swamp monster at bay. Enjoy!