Not too weak, not too powerful – finding the one that is JUST right
Pool pumps are an integral element of your pool’s filtration system. They circulate water through the pool filter system mixing chemicals and sanitizing the water to help keep it clean. You might think that a higher horsepower pump is always better, but that is not true. A pump that is too highly powered will completely bypass the filter altogether (creating a dirty pool) and put excessive wear on your filter and other pool equipment. Contrastingly, a pump that is too weak and lacks the power needed to circulate your water properly will not keep the water clean and algae can begin to grow. Just like Goldilocks, you need to find the pool pump that is JUST right – so how do you do that?
Determine Your Pool Volume (a.k.a. how much water your pool holds)
The first step is to calculate how much water your pool holds. This number is important because your pump should be able to turn over that amount of water every 8-10 hours. Check the paperwork that came with your pool to see if states how many gallons your pool holds. For inground pools, you may need to use some easy math calculations to determine how many gallons your pool holds, but since above ground pools are often similar in size in shape you may be able to determine the number of gallons your pool holds simply by reviewing these charts below:
Determine Desired Turnover Time (a.k.a. what is the Gallons per Minute Rating)
The next step is to determine the desired turnover time, which is how long it takes for the pool pump to cycle all the pool’s water completely. An ideal turnover time is 8-10 hours. To find this number, first figure the Gallons Per Hour (GPH).
Pool Volume in Gallons ÷ 8 hrs = GPH Example: 23,000 gallon pool ÷ 8 hrs = 2,875 gallons per hour
Since most pool pumps come with a Gallons Per Minute (GPM) rating, you now convert the GPH to GPM. Here’s the formula to do that:
GPH ÷ 60 minutes = GPM Example: 2,875 gallons per hour ÷ 60 minutes = 48 gallons per minute
In our example above, you will want a pump that can pump about 48 gallons per minute.
BUT NOTE: As mentioned earlier, the typical desired turnover rate is between 8-10 hours, so you can get a range by completing the calculations above by substituting 10 where you used 8. This would allow a range of acceptable pumps instead of assuming only one option. See the example below:
- 23,000 gallon pool ÷ 10 hrs = 2,300 gallons per hour ÷ 60 minutes = 38 GPM
Therefore, to complete this example, you can look for a pump with a GPM range between 38 – 48 GPM to meet the desired turnover time of 8-10 hours for your 23,000 gallon pool regardless of what the pump’s horsepower is.
So, to review, use these formulas with your pool volume in gallons, and you will easily figure out the GPM rating you want for your pool pump to meet the desired turnover time of 8-10 hours.
Calculate Maximum Flow Rate
You’ve calculated the GPM range for your new desired pool pump so you may think that you’ll just want to buy the pump on the high end of that range with the highest horsepower, but that is what Papa Bear would do and you are Goldilocks remember? Picking the highest GPM and highest horsepower in this situation isn’t always the smartest move to get the pump that is JUST right.
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. This means that you can have a pump capable of moving 120 gallons of water per minute, however, if the 2-inch piping will only allow 73 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.
To determine the maximum flow rate for your pool, count the number of intake lines for your pool and refer to the common pipe sizes below.
- For each 1.5-inch intake line, the maximum flow rate is 42 GPM
- For each 2-inch intake line, the maximum flow rate is 73 GPM
- For each 2.5-inch intake line, the maximum flow rate is 120 GPM
- For each 3-inch intake line, the maximum flow rate is 160 GPM
Example: Two 2-inch intake lines = 73 +73 The maximum flow rate is 146 GPM.
Compare pump flow rate with filter flow rate
Before selecting your new pool pump, you’ll want to verify the GPMs (gallons per minute) your pool filter can handle. The GPM information is typically labeled on the filter housing or can be found in the user’s manual. It is essential to find out the GPM flow rating for your filter because you do not want your new pump to exceed that number. If your pump’s GPM exceeds that of your filter, the water in your pool will not be filtered properly and will with have a dirty pool. You will always want your filter’s GPM to be higher than your pump’s to alleviate any additional strain on the pump motor and to make sure your pool gets properly cleaned.
Find the right pool pump
Now that you are done with the calculations, it is time to start looking for the right pool pump to optimize your above ground pool. You can begin narrowing down pool pump choices according to your pool size, plumbing intake lines, and filtration systems currently in place. As you shop, refer to the technical specifications from the manufacturer of the pump to find one that matches these needs and you will be sure to be just like Goldilocks and find the pump that is JUST right.