What Size Pool Pump Do I Need

What Size Pool Pump Do I Need
What Size Pool Pump Do I Need

What Size Pool Pump Do I Need? Yeah. We are going to cover everything from pumps to filters, to lights to heaters, and everything in between.

He is very excited.

But we will be covering everything in-ground pools, selecting pumps, filters, chlorinators, skimmers, return jets, cleaners.

Diving boards slide – We will be diving into diving boards.– Oh, yeah.

It’s going to be super fantastic.

But it should be a fun fantastic voyage.

Buckle up.


The process of selecting pool equipment should start with a pool pump.

It’s the heart of the pool system after all.

The pump is what circulates the water to and from the pool.

What Size Pool Pump Do I Need

And this little dandy right here is a pool pump.

There are two components to a pool pump.

You have the wet end housing, which is where all the water is held, obviously, the wet end.

And then you have the electric motor, is where no water should go, because electricity and water do not mix.

Fire and ice.

And water comes in here through the in port, and out the out port.


Before we can select a pool pump, we have to find out some things about the pool.

Like the size.

Yes, like the size.

So the first thing we’ll do is determine the gallons.

Alright. For rectangle, you go:

he first thing we'll do is determine the gallons
What Size Pool Pump Do I Need?-the first thing we’ll do is determine the gallons

Length x Width x Average Depth x 7.5 For a round pool, you go Diameter x Diameter x Average Depth X 5.9

For oval pools, Longest Diameter x Shortest Diameter x Average Depth x 6.7

And for those kidneys, Length x Average Width x Average Depth x 7.0

Now that Rob has us swimming in numbers, let’s work with a real-world example to try and figure this out.

Let’s say we have a 16 by 32-foot pool,16 foot wide and 32 feet long, and we’re going to figure out what the average depth is.

Now the deep end is going to be eight foot, shallow end is going to be four foot.

In order to average that out, we need to add the eight-plus the four, which gives us 12 and then divide that by two, which will
leave us with an average depth of six feet.

rectangle pool example
What Size Pool Pump Do I Need?-rectangle pool example

– Sweet example, broseph.

Now, let’s plug those numbers in and calculate our gallons.

32 foot long x 16 feet wide x 6 foot average depth x 7.5 equals 23,040 gallons.

calculate gallons using rectange fool formula
What Size Pool Pump Do I Need?-calculate gallons using rectange fool formula

– Wow. That’s good.
– I know.

– Well, you’re a regular Bobby Fisher.
– Yes, I am.

The goal of any residential pool is to turn over your body of water once a day.

The general rule is 8 to 10 hours.

That’s the pump run window you want to go for.

In this example, we will use eight hours.

Alright. And once you know gallons to turnover rate, you can calculate the gallons per minute required to accomplish said turnover rate.

Step one: take the gallons and divide it by hours.

That gives you the gallons per hour.

In our example, it’s 23,040 divided by 8, equals 2,880 gallons per hour.

calculating turnover rate
What Size Pool Pump Do I Need?- calculating turnover rate

Now you move that into step two: you do gallons per hour divided by 60, and that gives you gallons per minute.

So, in our example, it’s 2,880 gallons per hour, divided by 60, and this equals 48 gallons per minute.

Next, we will determine the total dynamic head of your plumbing system, also known as the TDH.

It’s the measurement of resistance working against your pump as it pulls water from your pool basin and then pushes it through your filter and back to the pool again.

The higher the dynamic head, the larger the pump and pipe you’ll need to offset the pressure.

Yes. Elements that’ll affect your dynamic head are the pipe size whether it’d be an inch and a half or two-inch, the length of the horizontal pipe, the rise of the water, the turns through the pipe, through any 45 or 90-degree elbows.

Valves and couplings will add to the feet of head.

Filters, heaters, and even the eyeballs in your pool can add to the feet of your head.

So basically, everything.

– The whole rigmarole.
– The whole rigmarole, yes.

Also, keep in mind that plumbing will determine your maximum flow rate.

For each one a half-inch intake line, the maximum flow rate is around 51 gallons per minute.

For each two-inch intake line, it can handle up to 84 gallons a minute.

Yes. To save us a whole lot of time and headache.

– And effort, in general.
– And effort.

We’ll use 60 feet of the head moving forward for our example.

If you like to calculate your own feet of head or look further into this, we have a blog on this very topic, written by this guy.

This guy.

Okay, we’re finally to the point where we can use gallons, turnover rate, and feet of head to select the horsepower of our pool pump.

Now, each pump will have a correlating pump curve, and with this pump curve, we can select the correct horsepower.

This chart is very easy to use.

The feet of head is listed along the Y-axis.

Y to the sky.

And the gallons per minute are listed along the X-axis.

The point at which these two lines intersect will correspond with a particular horsepower.

If it falls between two different horsepower lines, go with the higher of the two, otherwise, the pump won’t be strong enough for the turnover rate.

In our example, the 48 gallons per minute and the 60 feet of headline meet right below the one-and-a-half horsepower.

So that should be enough for our pool.

Now, this pump curve pointed to one and a half horsepower, but the horsepower flow ratings can vary from model to model, so make sure that you take a look at the pump curve for whatever model you’re interested in.

Okay. We’d like to say that once you’ve found the correct horsepower for your pump that you’d be done, but let’s pump the brakes a little bit.

That’s dad jokes 101 right there.

Who doesn’t love a good dad joke?

Dad jokes are like cowboy hats.

I hate them.


Well, there are still three different types of pumps to choose from.

You have single speed, dual speed, and variable speed.

Let’s start with the basic overview of each type.

The most common type is the single speed pump.

single pump speed
What Size Pool Pump Do I Need?- single speed pump

This pump operates at a single speed of 3,450 revolutions per minute, or RPM.

– Acronyms.
– Yes, they’re fun.

This kind of pump has the lowest upfront cost, but the highest operational cost.

Next up, we have the dual speed.

dual speed pump
What Size Pool Pump Do I Need?-dual speed pump

This pump operates at a high and a low speed.

High being 3,450, low is 1,725.

This pump has a more expensive upfront cost when compared to the single-speed, but it can save you about 50% on the electric bill.

Another benefit to running at a low speed is that it’s very quiet.

And who doesn’t love a quiet pump?

Yes pumps are like children. Always quiet.

Yes. Well.

– You’d wish.
– Yeah.

Finally, we have a variable speed pump.

 variable speed pump
What Size Pool Pump Do I Need?-variable speed pump

This pump can operate at a full range of speed from 600 RPM to 3,450 RPM.

It has the highest upfront cost, but it’s by far the least expensive pump to operate.

This pump is great for situations where you have water features, or maybe a spa.

For instance, you can run the pump at a low RPM to circulate the water through the pool, kick it up a little bit to run that waterfall, and then kick it all the way up to run those nice massage jets in your spa.

For more information regarding the differences between these pumps, check out our very well-written blog.

Yes. It’s a great read.

It is a great read.

– I think Patrick wrote it, right?
– I believe he did.

– Yes. Handsome guy.
– Yes.

He’s also our boss.

Now before we wrap this up and put a bow on it, we have to discuss the possible need for a second pump.

Yes. Maybe you have a spa with lot of jets.

Those jets require additional flow, so you might need a second pump to add that extra flow.

Another one would be water features, maybe a slide or a big waterfall that requires.

A very large Slip ‘N Slide?

A very large Slip ‘N Slide, if you had that

– 500 feet long.
– Yeah, yeah.

You got a big backyard, or you’re just in Texas and like big things.

Why not? Go for it.

Go big or go home.

Maybe you have a pressure cleaner that requires a booster pump so that would be a second pump.

– Yes, like a Poolvergneugen? – Yes, something like that.

I just love saying that word, electro.


But I’m pretty sure that covers everything in pumps.

I think so.

You’re you… Are you?

– I think I’m good.
– Okay.

– I’m great.
– Yeah.


Well, it’s time to pack it up, party people,and head on down to Filterville.


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