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Water Softener Sizing

Posted by JayhawkFan1988 (My Page) on
Tue, Jan 1, 13 at 20:41

Hello! I've been reading some of the posts on this forum (and a couple of others) about water softener sizing and feel I need some help. We have a Sears water softener that was installed 7 years ago and has recently failed. I understand that with the Sears and big box store units 5-7 years is approximately the lifespan to be expected, so I am preparing to purchase a new unit. Our water has the following characteristics:

Hardness: 21 gpg
Iron: .011 Mg/L
Manganese: .0027 Mg/L
pH: 7.1

Our incoming water line is 1" and a flow rate taken at a yard stand teed from our main water line with 3/4" line was 15gpm. We have 3 1/2 baths with a Jacuzzi tub and a multi-head shower. There are 4 people living in our home.

I'm not sure I understand all of the variables, but after looking at some available models I have some questions and would appreciate some learned opinions.

It appears flow rate is limited by the cubic feet of resin in the system. Should I be looking at a 2.5 cubic foot system to maximize my available flow rate? If so, is the Fleck 7000SXT an appropriate valve? How often should a system regenerate? It appears that with 4 people each using approx 60 gallons of water per day that somewhere between 35000 and 40000 grains would be appropriate for a once per week regen. That would seem to indicate that a 2.5 cubic foot unit is too large except for the flow rate.

Thanks in advance for any opinions!


Follow-Up Postings:

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RE: Water Softener Sizing

Based on your #s a 2.5 cube softener would be about right. Set up for efficiency you want to go about 7 days between regens and will have sufficient SFR for all the bathrooms and the big tub and uber-shower.

A Fleck 7000SXT is a good choice.


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RE: Water Softener Sizing

Jayhawkfan - A 2.5 cuft softener only appears too large because you are looking at the absolute maximum capacity of 80,000 grains. However, while this is technically true, it is only possible if you regenerate with a very high amount of salt.

We like to size softeners to be as efficient as possible and hit the sweet spot between salt usage and water usage. That spot is about 6 lb of salt per cubic foot of resin, regenerating every 7 days.

When we decrease the salt dosage to the softener during regen, it also decreases the capacity of the softner. At 6 lb of salt per cubic foot of resin, a 2.5 cuft softener has a capcity of 52,500 grains. When we take into account the required safety factor to ensure you never run out of soft water, that brings the capacity to 44,600 grains, which is right where you need to be.

You could get away with a 2 cuft softener, but will be better off with the 2.5 cuft size since you have a jacuzzi tub and multi-head shower.


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RE: Water Softener Sizing

Hello again! I wanted to thank you both for your help. Although it has taken me longer than I anticipated before, I have purchased and installed the 2.5 cuft softener with the Fleck 7000SXT valve. The installation went well, and the unit is up and running. I have set the programming parameters, but wanted to check my programming against your opinions.

I have set the following:

DF GAL
VT dF2b
CT Fd
C 50000
H 21
RS SF
SF 15
DO 9
RT 2:00
B1 10
BD 60
B2 5
RR 10
BF 40 (the unit has a .125 gpm blfc)
FM t1.2

I basically used the defaults except for capacity at 50000, hardness at 21, safety factor at 15, day override at 9 and Brine Fill at 40. I arrived at 40 for brine fill by calculating that I need 6 lbs of salt per cuft for a total of 15lbs, 5 gallons of water which dissolves 3lbs of salt per gallon, and 40 minutes draw at .125 gallons per minute. Also, I set the day override to 9 days which I think with our water usage pattern will be close to when the unit should regen based on capacity. Is 9 days OK, or too long?
Does the rest of the programming sound correct to you?

Thanks again for you help!


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