How to Select an Inground Pool Pump

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Let’s start with the gallons. There are calculations available for each shape. Here are a few common examples.

Rectangle - Length x Width x Average Depth x 7.5
Round - Diameter x Diameter x Average Depth x 5.9
Oval - Longest Diameter x Shortest Diameter x Average Depth x 6.7
Kidney - Length x Avg. Width x Avg. Depth x 7.0

A real example will help us moving forward. Let’s say the pool is a rectangle that’s 16’ wide and 32’ long. The deep end is 8’ and the shallow end is 4’. To get the average depth, add the deep end and shallow end depths and divide that total by 2. This gives us a 6’ average depth.

Now let’s plug those numbers in and calculate our gallons. 32’ long x 16’ wide x 6’ average depth x 7.5 equals 23,040 gallons.

The goal of any residential pool is to turn over the body of water once a day. The time it takes to turn the water over is known as the turnover rate. A standard turnover time is 8-10 hours. We will use 8 hours for our example.

Once you know the gallons and turnover rate, you can calculate the gallons per minute required to accomplish desired turnover rate.
Step One - Gallons (23,040) divide by Hours (8) = GPH (2,880)
Step Two - GPH (2,880) divide by 60 = GPM (48)

Next we will determine Total Dynamic head of your plumbing system . The TDH is the measurement of resistance working against your pump as it pulls water from your pool and then pushes it through your filter and back to your pool. The higher the dynamic head the larger the pump and pipe you will need to offset the pressure.
Elements that affect your dynamic head are:
-Pipe size (1-1/2” or 2”)
-The length of pipe horizontal pipe
-The rise of the water.
-The turns in the pipe 45 and 90 degree
-Valves and couplings
-Pool equipment, i.e. filters, heaters, eyeballs.

Keep in mind that the plumbing will determine your maximum flow rate. For each 1.5” intake line, the maximum flow rate is 51 gpm. Each 2” intake line can handle up to 84 gpm

We’re finally to the point where we can use the gallons, turnover rate & feet of head to select the HP of the pool pump. Each pump will have a correlating pump curve. This pump curve will point to the correct HP.

This chart is easy to use. The feet of head is listed along the y axis and the gallons per minute is listed along the x axis. The point at which the two lines intersect will correspond with a particular HP. If it falls between two different HP lines, go with the higher of the two. Otherwise the pump will not be strong enough for your turnover rate.

In our example, the 48 gpm line and 60’ of head line meet right below the 1.5HP curve. So the 1.5HP pump work for our example. Now, this pump curve pointed to 1.5HP but the HP will vary from model to model so make sure you look at the pump curve of each one.

We’d like to say that once you’ve found the correct HP for your pump that you’d be done but lets pump the brakes a little bit. There are still three different types of pumps to choose from. You have single speed, dual speed and variable speed pumps. Let’s start with a basic overview of each type.

Next up is the dual speed pump. This pump operates at two speeds; 3450 RPM and 1750 RPM. This pump has a more expensive up front cost but it can also save you up to 50% on operational costs over the single speed pump. This is due to the pump pulling lower amps when it’s in the low speed. Another benefit to running it on low speed is that it is very quiet.

Finally, we have the variable speed pump. This pump can operate at a full range of speeds from 600 RPM to 3450 RPM. It has the most upfront cost but it is by far the least expensive pump to operate. This pump is great for situations where you have water features or an attached spa. You can run the pump at a low RPM to circulate the water, then kick it up a little bit to run a waterfall and then kick it all the way up to a higher RPM to run the message jets in the spa. For more information regarding the differences between these pumps check out our blog.

[leslieziegler]

Fantastic videos! Thank you for simplifying this process!!

[hperez]

Hi guys. I love watching your videos they are so helpful and easy to understand. Thank you guys

[Giggidygiggidy]

Great video guys except for the audio. It is way too low. I have it on max and it's hard to hear you guys, and no my hearing is not bad

[salvadorreciosada]

Great video! Congrats!... What is the average pipe size for a standard rectangular house pool?

[jeffreygenerelli]

What would be the calculating formula for an L shaped pool?

[whitephoenixfire]

How do we choose between pumps marketed as in vs above ground? I have a 12x28 inground but most properly sized pumps for my size are listed as above ground. If the max head on an above ground pump is between the 50-60 head ft needed for my pool, would those above ground 1.5hp/50 head pumps be correctly sized? 1.5" lines existing.

[omargarcia]

Hello I have a question . My pool pump turn on and then after like 20 minutes turns off and sometimes works fine what can it be ? Thanks in advance

[sullyd]

Guys, my lacrosse filter is leaking through the new lid and ‘o’ ring . I’m presuming it’s the thread on the filter. What can I use to fix this. Can’t buy a part for a new thread. Is there something that will sort this problem,

[bbyevou]

Is it worth going with 2.5" pvc plumbing for 40, 000 gal pool or is 2" more then enough?

[G_Grip]

I have acquired a pool with the recent purchase of my house. Not sure on how the plumbing is run. Also, the pool is an odd shape. I would like to change the sand filter to a canister in the process of changing the pump. So.... with all of the unknowns, how do I go about sizing my pump? Is too big of a pump a problem besides the increase in the electric bill?

[MarvinMr]

Hello I have an 8 ft deep pool that I want to add a waterfall to. Thing is that I do not want to run the waterfall thru the motor. I would like to use a smaller motor so that I can take it on and off whenever I feel like it. What type of motor would you suggest? I was looking at the intex pumps for above ground pools. Would they be powerfull enough? Thank you.

[lrosario]

Good morning! I have a question about my pool pump and filter system, We have the Magnum Jacuzzi pump, which by the way it's really old, now, We want to change the pump to a more update it one, We're looking at the Hayward Tristar Max Rate 1.5, but We don't know if it'll match with our cartridge filter? our pool is 15X30, 20, 000g. any help would be gratefully appreciated. thank you.

[AbhayAggarwal]

My pool is only 3000 gallons. What do I do?

[muhammedmahmood]

It would be better if you could have add some more details about calculating TDH

[paulr]

Can anybody advise about horse power and what is best for what?

[cnysmitty]

Good basic information, HORRIBLE delivery.