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How to Calculate Flow Rate

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Categories: Filters, Pumps
 
To determine your your flow rate, there is an equation that allows you to figure it pretty easily and accurately. You will need a vacuum gauge and a working pressure gauge on your filter.
  • The vacuum gauge should have a 1/4" MIP nipple on it. This is threaded into the front port of your pump located near the bottom. Many pumps have two, so be careful that you get the front one. This vacuum gauge will read the inches of mercury that your pump develops when it is running. 
 
The equation goes like this:
  • The reading from the vacuum gauge is multiplied by 1.13. 
  • The reading of the pressure gauge is multiplied by 2.31. 
  • Add the two together and you will get a number that reveals the Total Dynamic Head (TDH). 
 
With this number you must go to the flow rate chart for your pump. We list the pump's flow rate charts on most of our product pages. If yours is not there, then the owner's manual will have it. We also have most of the pump owner's manual on the product pages as well. You cannot use just any pumps flow rate chart, it must be for your pump that you've collected the information above for.
 
The flow rate chart will have GPM at the bottom of the chart and a TDH calibration with a range starting at zero and going upwards on the left. Using the number you calculated, travel upwards on the chart from the GPM, until you meet at the intersect of the TDH number. That intersect number is how many gallons of water and how hard it is pushing.
 
 
 
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