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Pool Pumps> Choosing a Pool Pump:  |  Turnover Rates  Pool Features  |  Pool Plumbing  |  Pool Equipment   |  Pump Options  |  Hydraulics  |  Pump Curves

Pool Flow Rates

The first job of the pool pump is to circulate the pool water through the filter and back out to the pool. To do so, the pump must have a minimum flow rate in GPM (gallons per minute) that will allow it to move all the water through the filter within a given amount of time.. 

To determine the minimum flow rate you must do two things:

Determine the capacity of your pool in gallons.

Rectangular Pools - Length x Width x Average Depth x 7.5 = Gallons in Pool

If the pool is 30 feet long by 18 feet wide by 4.5 feet deep, the approximate pool volume is 18,225 gallons.

(30 times 18 times 4.5 times 7.5)

Length Width Avg. Depth 7.5 Gallons
30 18 4.5 7.5 18225
25 16 3.5 7.5 10500

Round Pools - Radius x Radius x 3.14 x Average Depth x 7.5 = Gallons in Pool

If the round pool has a 14 foot radius, and a depth of 4.5 ft. then the approximate pool volume would be 20.771

(14 times 14 times 3.14 times 4.5 times 7.5)  REMEMBER: Radius equals diameter divided by 2.

Radius2 3.14 Avg. Depth 7.5 Gallons
14 x 14 3.14 4.5 7.5 20771
12.5 x 12.5 3.14 3.5 7.5 12878

Determine the desired turnover rate.

In other words, how long should it take to move the entire contents of your swimming pool through the filter.  Divide the pool gallonage by the turnover rate to determine the minimum flow rate per hour.  Divide that number by 60 to determine the minimum flow rate per minute.

Gallons In Pool

Flow Rate Required for Proper Turnover

6 hr. turnover

(high use)

8 hr turnover

(medium use)

10 hr turnover

(low use)


27.8 20.8 16.7


41.7 31.3 25.0


55.6 41.7 33.3


69.4 52.1 41.7


83.3 62.5 50.0


111.1 83.3 66.7


138.9 104.2 83.3


277.8 208.3 166.7

If the pool holds 20,000 gallons of water and enjoys a medium level of usage, you would look at the 20,000 gallon line and go to the 8 hour turnover column (for medium use).  You would find that the pool requires a 41.7 gallon per minute flow rate to achieve proper turnover.  You can look at the pump charts to find out the pump that will deliver that level of performance.

Not sure what size pump you need? Request a FREE PUMP SIZE recommendation  specifically for your pool.

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