# Kinetico Q237?

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#### Gary Slusser

##### That's all folks!
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?
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 Slusser

##### That's all folks!
In your 1st statement you said and I quote, "Well that is the gpm you get IF you'll suffer a 15 psi pressure loss". The word "IF" implied that "IF" you lost 15 psi the GPM would be X.
I don't understand, that is what it means, IF the person is willing to suffer a 15 psi pressure loss they will be getting X gpm through the softener. Or, IF they run X gpm through the softener, they will have a 15 psi pressure loss.

What else do you think it means?

And yes I know how it works.
Then why the above?

If the "V" (water does not pass through the resin in a linear form but rather a "V" shape) reaches the distributor, you have hardness bleed through. Any 1st year study learns that.
ummm that's why I always use a gravel underbed. I guess you don't.

And that still does not explain how out of the thousands of people that I have tested there water when I was there of service, salt delivery or just a routine check up di not have hard water unless the unit was not working. No matter how fast they ran the water. I have not run across a house yet that exceded the flow rate. I have seen it is a commericial business.
You still don't understand what I'm talking about, you didn't run more gpm through the softener than the constant SFR gpm and as the water is running collect the sample and test it.

If you still don't agree, call a resin manufacturer and ask them about it. Or figure out what the spec sheet figures mean.

#### Gary Slusser

##### That's all folks!
When a unit says x gpm @15 psi mean you lose 15 psi @ x gpm through the resin.
It means you lose 15 psi across the whole softener.

As far as gravel, again you are wrong. Getting to be a habit with you. The purpose of the gravel (underbedding) it to protect the distributor. Nothing more.
You believing that, it's OK with me.

And yes I do understand what you are talking about. If you pass too much water the "V" will be at the distributor and you get hardness bleed through. This is because of lack of bed depth. The SFR is the rate at which resin can remove hardness. If it is that important, then tell all of us why manufactors size units they way they do.
When sizing a softener, how do you determine how much water is too much?

Yes it is a lack of bed depth and the only way to get more bed depth is to use a larger softener.

You are proving my point.

How do manufacturers size softeners if not by bed depth; starting with a 6" x 18" resin tank, each succeeding larger size softener has a larger tank and more resin and that means more bed depth, right?

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Hey, wait a minute.

This is awkward, but...

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