Determining the correct size filter and pump for your pool starts with understanding how much water needs to be circulated and filtered. This required circulation rate is often measured in Gallons Per Hour (GPH) or Gallons Per Minute (GPM).
Calculating Your Pool's Required Flow Rate (GPH & GPM)
A standard method to estimate the necessary flow rate for your pool filter and pump system is based on your pool's total volume. This calculation helps ensure the entire volume of water is processed by the filter within a reasonable timeframe, typically aiming for an 8-hour turnover cycle.
Here's the calculation based on your pool's volume:
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Calculate Gallons Per Hour (GPH):
- Divide your pool's total volume (in gallons) by 8. This gives you the target flow rate in gallons per hour.
- Formula:
Pool Volume (Gallons) ÷ 8 = Required GPH
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Calculate Gallons Per Minute (GPM):
- Once you have the required GPH, divide that number by 60 (because there are 60 minutes in an hour). This converts the target flow rate to gallons per minute.
- Formula:
Required GPH ÷ 60 = Required GPM
Example Calculation
Using the example provided:
- Assume your pool is an average size, approximately 20,000 gallons.
Following the steps above:
- GPH Calculation: 20,000 gallons ÷ 8 = 2,500 GPH
- GPM Calculation: 2,500 GPH ÷ 60 = Approximately 42 GPM
So, for a 20,000-gallon pool, you would aim for a filter and pump system capable of handling approximately 2,500 GPH or 42 GPM.
Applying the Calculation
The calculated GPH and GPM represent the minimum flow rate your pump and filter system should be able to achieve to effectively circulate and clean your pool water within the desired timeframe (around 8 hours).
When selecting a filter and pump, you will look at the manufacturer's specifications. Pumps are rated by GPM and GPH, often shown on a "pump curve" that indicates flow rate at different system pressures (known as "head"). Filters also have maximum flow rate ratings. Your chosen pump and filter must be appropriately sized to handle the calculated flow rate for your pool's volume.
Understanding your required flow rate is the essential first step in selecting appropriately sized pool equipment.
