It's a question that we get all the time here at Aquatell -what is the flow rate that a water softener can handle? Customers don't know it when they ask it but this is actually two questions in one. Here's why:
There's the flow rate that you can physically push through a softener not worrying about the softness of the water that exits the machine.
Then there's the flow rate that you expect a softener to handle while providing you with soft water.
The reason for much of the confusion around this question is because many (actually most) water softener retailers state the maximum flow rate you can physically push through the softener (number 1 above) in the tech specs of their machines. Why? Because it's a bigger number and sounds better.
But it's much more accurate and responsible to use the flow rate that can actually besoftenedby the machine as the specified flow rate. This flow rate is determined by the amount of resin that a softener is built with. For hardness levels that aren't in excess of 50 grains per gallon (855 mg/L) a softener can produce about 5 U.S gpm of soft water flow for every cubic foot of resin the softener is built with.
That's another reason why here at Aquatell we describe the size of all of our softeners in terms of cubic feet of resin used in the build.