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What Size Pump Should I get for my Pool?

If you’re looking to build a new pool or simply looking to replace a pool pump you may find yourself asking, “Is a larger horsepower (HP) pool pump always better”. However, it’s important to know that pool pumps should really be rated by the gallons per minute of water flow instead of the motor’s HP.

What you’re looking for is a pump that will be able to pump all the water in your pool through the filter in no more than 8-10 hours. This typically looks likes 40 GPM (gallons per minute) for smaller pools and 80 GPM for larger pools. However, you can determine the more precise needs of your individual pool by following these steps:

  1. Determine how any gallons of water your pool holds. You can use out Swimming Pool Gallon Calculator here. For this example, let’s assume that your pool holds 24,000 gallons of water.
  2. Determine how many gallons you need to pump per hour to clean all the water in your pool in eight hours. Divide the gallons of water your pool holds (answer from step 1) by eight. Using the example number of gallons previously given, this equation would look as follows:
    • 24,000 gallons ÷ 8 hours = 3,000
  3. As pumps are labeled with how many gallons they move per minute, you’ll now need to divide the above number by 60 (as there are 60 minutes per every hour).
    • 24,000 gallons ÷ 8 hours = 3,000 ÷ 60 = 50 GPM (gallons per minute)

Keep in mind that the desired time frame of turnover is between 8-10 hours, so you get a range by substituting the 8 hours used above, for 10 hours instead. This would allow a range of acceptable pumps instead of assuming only one options.

  • 24,000 ÷ 10 hours = 2,400 ÷ 60 = 40 GPM (gallons per minute)
  • You’re now looking for a pump with a GPM range between 40-50 regardless of what the HP is.

ADDITIONAL FACTORS

  • The GPM of the pump will go down the farther away the pump is in relation to the pool. Valves and PVC turns will also restrict the pumps GPM.
  • Extra water features like spas, fountains, waterfalls, etc. will require a higher GPM rate which equate to a higher HP pump.

GOOD TO KNOW:

Your pool pump’s GPM will directly relate to your pool’s filter GPM. You’ll want your filter’s GPM to be higher than your pumps to alleviate any additional strain on the pump motor.

While some may think it’s just easier to go with the highest GPM and HP and not worry about anything further, note that your pool’s pipes can only take so much movement and pressure based on their size. For this reason, each pool has a maximum flow rate, which is determined solely by your pool’s pipes.

  • 1.5-inch intake line, the maximum flow rate is 42 GPM
  • 2-inch intake line, the maximum flow rate is 73 GPM
  • 2.5-inch intake line, the maximum flow rate is 120 GPM
  • 3-inch intake line, the maximum flow rate is 160 GPM

This means that you can have a pump capable of moving 100 gallons of water per minute, however, if the 1.5-inch piping will only allow 42 gallons per minute you risk damaging your system by creating too much strain on your pump that cannot move water as quickly as it’ll be trying to.

Your pool will most likely have multiple sizes of piping. You’ll want to err on the side of caution and use the smallest piping for your pool’s maximum flow rate. For example, if you primarily have 3-inch pipes in the plumbing system of your pool, but also have a spa with a 2-inch plumbing pipe, you’re maximum flow rate would be 73 GPM.

GREEN & ENERGY EFFICIENT:

There are ways to get the most gallons per minute from your pool pump with the least horse power motor. Increasing the PVC pipe size from 1-1/2″ to 2″ will increase any pumps GPM. Other options to make your pool pump more efficient are:

  1. Include a pump timer
  2. Opt for a pump with a 2-speed motor
  3. Invest in a newer variable speed pumpintelliflo
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77 Comments

  1. mikey g says:

    My pool 2hp pool pump just died after 15 years of maint free service Yes I said maint free Im looking for a replacement and a few sales people have told me that todays 1 1/2 hp motors are better and more efficient than a 15 yr old 2hp is this true?

  2. Rich Landucci says:

    Hi!
    I have an in-ground, 10,000 gallon, pebble tec pool built by Shasta Pools in 1997. We also had Shasta build us a 7 ft. diameter x 3 ½ ft. deep (approx.) spa and a good size water feature. We have two single speed pumps. A 2 HP runs the pool and spa, and a 1/ ½ HP pump runs the water feature.

    With that said, a couple days ago, the 2 HP pump started “screaming” almost immediately after start up. Icleaned- out every skimmer and checked the system for proper water flow, obstructions, etc……all okay. I had the pump. This pump was last replaced about 4 years ago.

    While surfing the net for pumps, I came across your sight and found it very informative, well written, and seemingly with honest and unbiased. I’m hoping that with the information I have provided to you that you could help me determine #1. What type pump (variable or single speed) I need. #2 What HP would be appropriate #3 What manufacturers have better track records #4 Who sells them with reliable competitive prices. And, #5, and other information that would be helpful to buyers in these terrible financial times.

    I hope that I am not asking for an exceedingly large amount of information and whatever you can pass along to me is very gratefully appreciated. I would like to thank you, in advance, for your help with any information you can provide me with. It is greatly appreciated.

    Sincerely,

    Rich Landucci

  3. Scott says:

    Rich

    The answer is it depends on several factors but most often it is best to go back with the same HP.

  4. Maria Williams says:

    We are new home/pool owners to a 13 year old approx pool. We have a 14 x34 3 to 5 ft fiberglass in ground pool with a 1 hp 110 volt Pentair pool pump. We live in south texas, have no trees in the backyard but do have a lot of dirt from the local area from farming. We bought a Kreepy Krauly sandshark pool cleaner and do not see it move in the pool. We have suction on the wall and in the 1 and only skimmer but not enough for the pool cleaner. We ordered a new DE filter since we were not sure when they were changed. Any help would be appreciated. I don’t think we have an air leak in the hose since we don’t see any bubbles, but please help. Something we can figure out or get professional help locally?????

  5. Pearl Mary says:

    I had a leak at the pipe just above the pump. The repairman told me that my pump was going out and I needed to replace it. So I did. When I asked if the pump was 1 1/2 HP he replied 3/4. He then said that my pump was too big and a 3/4 was better. Not knowing any better I didn’t question him. However, after more thought I was became very concerned.

    Seven Years ago, after hurricane Katrina, I had to replace the pump. So I purchased the same kind of pump that was there. There was a 1 1/2 hp. My pool is 15,000 gal. and it is 3ft to 6ft deep. It is a kidney shape. My questions: is it really good to have a smaller pump? Will I have to run the pump longer? Will it save money?

  6. Greg says:

    Pearl,

    A smaller pump really is better. A 3/4hp or 1hp pump will allow you to run the pump longer while increasing your energy savings. It will also allow you to push water through the filter more slowly which will allow the water to filter more thoroughly and efficiently. There are other things to consider when purchasing a pump for your pool though. If you have water features such as a slide, waterfall, deckjets, or other things, you may need a bigger pump in order to get the right performance out of those water features.

  7. Greg says:

    Maria,

    Congratulations on your new home and pool! I know keeping your pool clean can be quite a task. On page 13 of the installation manual for the sand shark (Click here for Installation Manual) there is a troubleshooting guide that may help you. If it does not help, Pentair may be able to assist you in pinpointing why the cleaner is not operating properly.

  8. Lee Ann says:

    Our pool pump made a very loud humming noise when we first turned it on this summer. I was moving some leaves from around it and it was so hot I burned my hand. I contacted our pool store and he said it sounded like the pump was getting ready to go out and it was ok to keep it running until then. Someone gave me a Dayton Pool pump-brand new- that is 1/2 HP. Our pool hold approx. 25,000-30,000 gallons of water. The shallow end is about 3 ft deep and deep end is about 10 ft deep. Do I need a motor with a high hp on it?

  9. Greg says:

    Lee Ann, a smaller HP pump like the 1/2 hp would probably be a little bit undersized for a pool that is 25,000 to 30,000 gallons. However, that pump would probably work just fine for the pool!

  10. Sheila says:

    I have a 5 foot 28 round intex pool, and I am wanting to upgrade it alittle. I wanting to put a 1 hp pump & 16″ sand filter on it will this work.

  11. Laci Carnes says:

    Hello Sheila!
    The best upgrade filter system that will allow for easy upgrade on the intex pools would be the 12″ Bluewave Sandman! You can read more about it here-
    http://www.royalswimmingpools.com/BlueWave-Sandman-12-Inch-Filter-with-1-2HP-Pump.html

  12. These are some great pieces of advice; after all, when you’re buying a pool pump you want to make sure you’re getting a good one. I particularly like the article’s advice about choosing one that is rated by gallons per minute. That way you can get a much better idea of how much water is being cycled through your pool.

  13. Harold says:

    How do I know if I have a leak in the pipes?

  14. I agree that it would make sense for pool pumps to be rated by the gallons per minute rather than the horsepower. After all, if you know how many gallons your pool holds, that would make it easy to find the right type of pump right? I have no idea how many gallons my pool holds, so I have to do a little more research before I buy a pump.

  15. Kenneth Burr says:

    My pool is 14×24, 4 feet deep oval. It’s above ground. The pump has stopped working. What’s an economical replacement?

  16. Laci Carnes says:

    Hello Kairi! You can try our Pool Gallon Calculator here! http://www.royalswimmingpools.com/Gallon_Calculator.htm
    Good luck!

  17. Laci Carnes says:

    Hello Kenneth! You can view our replacement pumps (starting as low as $159.00) depending on your preference type! http://www.royalswimmingpools.com/Above-Ground-Pool-Replacement-Pumps.html
    Thank you! Let us know if you have any further questions!

  18. marlene says:

    Hi! how many HP need a pool with18ft x32ft with 20 gallons of water. 1HP or 1 1/2 HP witch one is the correct HP

  19. Tpit says:

    We have a 24 ft pool, about 48 inches in center above ground. The motor went out on the sand filter and we replaced it with a 3/4 hp Hayward. The PVC are 2 inch. We are questioning if this motor is big enough? It doesn’t seem to be circulating the water and the pump runs basically nearly 20 hrs at a time. Any suggestions or insight? We would greatly appreciate it! Thanks so much.

  20. Laci Carnes says:

    Hello Harold,

    I believe this article will be a good resource in helping to determine if there is a leak in your pipes: http://www.royalswimmingpools.com/blog/how-to-find-leaks-in-vinyl-liner-pools/

  21. Jeff says:

    I am looking to get a sand filter for our 18 foot above ground pool that is 4 feet deep. We were wanting to go with hayward. Would a 18′ Sand filter be sufficient enough or should we go 21′?

  22. Laci Carnes says:

    Hi Marlene! So many other factors play a part in considering a pool pump than simply the number of a gallons in your pool. How far is the pump going to be located away from the pool itself? Further away means a higher HP. Do you have any water features? Yes- higher HP. If this is a typical 20k gallon pool with no water features and the pump is very close/right next to the pool you can use 1HP with little to no concerns. Otherwise I would opt for the 1 1/2 HP pump. Thank you!

  23. jeanni butler says:

    I need help… if any one could help me. I have a 17 ft x 52 in round above ground pool and a 1/2 hp sand pump is my pump big enough or should I get a larger pump?

  24. Laci Carnes says:

    Hi Jeanni!
    The general rule for above ground pools over 24 ft round, use a 1.5 HP pump. Pay attention to the maximum gallons per minute (GPM) of both your pool filter and pool pump though as your pump’s GPM should never exceed your filter’s GPM.

  25. Laci Carnes says:

    Hi Jeff! An 18′ should be more than efficient for your size pool. The benefits of the 21′ would just be the ability to cover more surface space if your pool is in an area that sees a lot of extra debris. Unless your pool sits under a fair amount of trees, I would rest easy with the 18′. Hope that helps!

  26. Laci Carnes says:

    Hello! Yes, it seems like your filter may be too small. They general rule for round above ground pools over 24 ft. is a a 1.5 HP. Hope that helps! Let us know if we can help order you a larger Hayward filter for your pool!

  27. Brent Knoll says:

    Gallons per minute are KEY! Thank you for sharing!

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