That's all folks!
With the exception of a 1.25', with each increase in volume, the tank diameter is increased. That spreads the column of resin out and you don't get the full benefit of all of the increased volume because it's the depth of the resin that counts. Going from a 9" to 10", then 10" for a 40K, and then a 12" and then a 13" shows the spread.Gary,
I have a question about the calculation of SFR--the max rate at which a softener will consistently produce soft water. In the above quote you say that it is determined by the volume of the resin in the softener. Elsewhere, including your website, you cite specific values for SFR for various volumes of standard resin. On your web site it is listed as "The SFR gpm of most softeners in gpm is: 1.0' cuft = 9, 1.25' = 10, 1.5' = 12, 2.0' = 13, 2.5' = 18, 3.0' = 20, 3.5' = 22 gpm, 4.0 = 25 etc.. ". If SFR were directly related to resin volume, and nothing else, I would expect that a 50% increase in resin volume would increase SFR by 50% and a doubling of the resin volume would double the resin volume. However that is not the relationship reflected in the figures. I am particularly puzzled by the fact that a 25% increase in resin volume, from 1 cubic ft to 1.25 cubic ft only increases SFT by 11%, while a 25% increase in resin volume from 2 cubic ft to 2.5 cubic ft increases SFR by 38%.
My question is why the SFR has such an erratic relationship to resin volume. Is it because there are other things that affect the number that are not specified? If so, what are they?