How long to run a pool water pump and filter

How long to run a pool water pump and filter

This is a very, very common question and the answer is “it depends.”

However, the quick and easy answer is 1 hour for every 10 degrees F of the temperature of the water.

More accurately though you should run it as long and as much as is required to keep your water clean and clear.

Let’s see if we can build an equation to help you figure out what works for your specific situation.

Geography and temperature

We have probably all thought “How long should a pool pump run?” at one time or another.

The largest variable in the answer to this question is the temperature of the pool water.

The warmer the water the better the environment is for algae and bacteria growth.

As a result, it’s important to circulate sanitizer more frequently to make sure that it reaches all areas of the pool and if you have an inline chlorine dispenser or saltwater chlorine generator then you need to have your pump running to keep the chlorine levels high enough to keep the water sanitized.

First 2 variables are (temperature + chlorine concentration)


The third important variable is debris, and depending on the kind of debris you could end up with different problems.

For instance, leaves that aren’t skimmed from the surface and caught in your skimmer basket can sink and cause staining on your pool floor.

So not only is it an eyesore to look at all those leaves on the surface, it can also cause staining and more work for you.

In some situations there are so many leaves that you have to use a net to scoop, a pool cover to prevent them from getting in the pool, or a surface skimming robot to keep up during the fall. 

If you are in an area where there is a lot of wind or rain that deposits dirt or sand then you may find that your pool surface stays dark or dirty and you need to keep the pump running enough to help filter out the dirt as you brush your pool (frequently, it’s like flossing your teeth – don’t skip it.)

In it’s least scientific form pump runtime is simply:  RT = T+CC+Cn

Sorry, couldn’t resist since we were told we would use it when we grew up, right?

Hang in there, we are almost done with this terrible analogy that hopefully makes sense in a non-mathematical sense.

So far we have (Temperature + Chlorine Concentration + Contamination)

Let’s call this our RT or “how long to run pool pump calculator” and see how it works.

Let’s solve for RT with an example:

It’s 90 F and the level of chlorine in the water is lower than the range needed and there the surface of the water looks good.

At 90 degrees Fahrenheit we have:

  • RT = (90/10) + (more time because there isn’t enough chlorine to stay within the desired range) + (0 because there surface is good)
  • RT = 9 hours + a little extra runtime (or maybe an adjustment on your chlorine method ir of debris) + 0


  • RT=11 hours

Of course that’s just a silly made up example to drive home the point that “it depends” and that it’s not always pump run time that solves the problem. However, the concepts are real and the first two variables really are big factors and this concept is an equation of sorts because the variables do change dynamically so your runtime can change as well.

Adding Chemicals 

You always want to add pool chemicals when your pump will be running for periods greater than three hours so that you get a good mix of chemicals.

(Three hours is an arbitrary rule of thumb, feel free to run it longer as it’s better to overshoot than undershoot in this case: turbidity).

Plumbing and pump size

The size of your pump, your pipes and your pool will factor into run time as well.

Now there really is a lot of math behind this and if you are interested then you can use a swimming pool pump size calculator, but that should have been done by the pool builder when they designed the pool.

If you are not a pool builder it’s easier to start with the 10 degree rule of thumb and adjust based on the concept behind the equation we simplified.

That was a lot of information and was likely confusing and maybe scary, but the key is to find a baseline and experiment from there to find the optimal configuration.

You have to consider the entire pool equipment ecosystem and the external factors impacting your water to find your magic RT. 

However, if that sounds like too much or confusing, Sutro can help you simplify it.

Our Sutro water Monitor will help you proactively keep your water balanced and we will even tell you when to make adjustments due to weather events.

Not only will we tell you when to make adjustments, we will even tell you what to adjust. 

We promise to help you love your pool (or spa) again!

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