You have to size for the maximum hardness so based on that info...

A 2.5 cu ft softener using 15 lbs of salt (6 lbs per cu ft) would regenerate every 7 days which is perfect.

You'd get more than adequate SFR and very efficient softener operation.

A 2.5 cu ft softener is too large for a 5600 so you'd be looking at a Fleck 2510SXT or a Fleck 7000SXT.

You could use a 2 cu ft softener but it would set up at a higher salt dose and not be as efficient. The difference in cost between a 2 cu ft and a 2.5 cu ft at time of purchase in small and the savings in salt would recover that expense in short order.

We should also now the TDS and PH of the water and has the water been tested for bacteria and nitrates?

Thanks for the info. Is it a big deal going from 3/4" pipe to the 1 1/4" on the 7000SXT?

I have to find the TDS and PH. Haven't tested for bacteria or nitrates. I think the town has some of this info on file. Could use that as a starting point.

No big deal going 3/4 to Fleck 7000 bypass.

7000 bypass should come with 1" NPT PVC connector. 3/4" to 1" adapters are EZ to find.

If you're on a town or municipal water system they should be dealing with nitrates and bacteria but best to be sure.

A fleck 9100 twin tank with 45k capacity (1.5 cuft) per tank would actually be the most efficient for this application.
This system would regenerate every 4.8 days at 11#'s of salt. 6000 grains per pound of salt is only theoretical, not practical. Typical grains recovery per# of salt are 3350 - 5100. A more practical application would be 4000 grains per# of salt. This application would result in 69#'s of salt use per month (836# per yr) and less total water usage per year. This system also uses soft water regeneration so it is more efficient at iron and manganese removal.
RJ

RJ,

Sorry, can't follow your math. You are entitled to your opinion but where did 6000 grains of hardness removed per pound of salt come from?

2.5 cu ft regenerated with 15 lbs of salt (6 lbs per cu ft) yields about 3300 grains of Capacity PER lb of salt (salt efficiency) not the 6000 you are dreaming up to argue against.

A properly sized and setup 2,5 cu ft single resin tank softener will use 60 lbs of salt a month which is more efficient than your twin in both salt and water use per month of regenerations. A 2.5 cube single will take up less floor space, offer greater SFR, have fewer parts AND fewer plumbing connections (2 resin tanks), and cost less. A 2.5 cube single resin tank softener will fit right in where the OP's Culligan used to be for an EZ install.

A twin is an option but there's really no reason. There's only a trace of iron and manganese. If the iron were higher the twin would be worth considering.

At 75k capacity and 15# of salt, efficiency would be 5000gpp of salt. But we know that is not practical. With their average daily water usage of 5x75=375 x 22gpg their daily hardness usage is 8250 grains. If system regenerates every 7 days (which was stated) that would only give 57,750 grains of capacity. This equates to 3850gpp of salt. This leaves 24% of total capacity in reserve, over 2 days reserve (inefficient).
A 2.5 cuft softener will use 195+ gallons of water per regeneration. 365 divide 7= 52 x 195= (10,140 gpy)
Yearly salt usage = 782#
1.5 cuft twin uses 120 gallons per regeneration and actually would regenerate every 5.3 days.
Yearly salt usage = 757#
3,975 gpp of salt efficiency.
365 divide 5.3= (8,264 gpy)
RJ

I'm not recommending ANYWHERE NEAR 75k more like 48k and that's @ 15 lbs gross salt dose or 6 lbs/cu ft..

Did you make the mistake of misreading the OP's iron and manganese test results were PPB and not PPM? That could be why your numbers are SO high.

RJ,

I find 60 gpd is more realistic for daily water use.

That's 48k from 2.5 cu ft @ 15 lbs (6 lbs/cu ft). So, let's do the math on that...

5 people x 60 gallons/day x 22 grains hardness = 6600 grains per day x 7days = 46200

So, 46200 divided by 15 lbs of salt = 3080 grains per lb of salt removed.

Where's the 6000 grain efficiency you're fixated on?

Now, 15 lbs of salt/week (and water used for only ONE regeneration a week) = 780 lbs/year or 19.5 bags x $4.00 per bag = $80 a year.

My numbers add up just fine... again and again and again and again.

Thanks so much for the info. Very educational. I've had 3 quotes, all undersizing the unit, although one did admit after some targeted questioning that the 2.5cu would be most efficient and cost effective. I don't think I've ever been undersold anything in my life :)

Now a follow-up. We would like to run drinking water through a filter system (RO) into the refrigerator. Will a 5-stage RO take any residual sodium out of the water? The water without the softener and through a softener (my parents house) tastes funny (compared to bottled filtered water). Family drinks a lot of water, and the water jug delivery is getting expensive to maintain.

I'm constantly amazed at how many water treatment pros offer undersized softeners rather than explaining to the customer why they should spend what they should spend and that the operating costs of the correctly sized softener will be less.

A 4 stage or 5 stage RO will give you exactly the same water as the Culligan water machine at WalMart (it is a BIG RO).

ROs filter pretty much everything out of the water except the H and the O. Get a good one made in the US. The no name Chinese ones tend to have problems that can manifest as a monster water leak.

RO ice cubes are GREAT... you'll love them.

great...I have an obsession with good ice. I wanted to install a clear ice maker in our remodeled kitchen...but the wife nixed that. Instead she...I mean WE got double ovens :)

A 2.5 cuft softener is 75k capacity. At 46200 capacity this would leave 29k as reserve or about 4 days reserve. That is very inefficient. 3080gpp is inefficient as well.
365 divide 7 = 52x15=752# per yr & 10,140 gallons of water used per year to regenerate.
Twin Tank 1.5 (45k) softener (no reserve capacity needed)
11# of salt yields 4000gpg.
44k divide 6600 = 6.6days between regenerations.
365 divide 6.6 = 55x11=608# per yr or 15 bags@ $4=$60 per yr
55x120 (gallons per regeneration) = 6,636 gallons per yr.
For this application a twin tank system is the most efficient for salt and water usage.
A reverse osmosis system is the best option for your drinking water. I would agree with JAL, get a good RO system you will not regret it and your family will drink a lot more water. Our family drinks 3-5 gallons of RO water per day at pennies per gallon. Once you have an RO you will never want to live without one again. The convenience, quality of water and quantity make it one of the best investments for a home. If you upgrade the storage tank to a 10 gallon tank you will have plenty of storage for periods of heavy usage.
Good luck and good water to you and your family,
RJ

RJ,

A 2.5 cu ft softener is ONLY a 75k softener when programmed at the MAXIMUM and least efficient salt dose of 15 lbs/cu ft.

EVERY softener has variable capacity (K) depending on the salt dose chosen. Few choose to recommend softeners set up for adequate SFR and efficient salt use while many do not.

You favor twin resin tank softeners, and while I acknowledge their advantages in certain circumstances, in ptyles' situation a single tank softener will work perfectly, reliably, and efficiently at a lower cost and with less complexity than a twin.

We will continue to disagree about softener sizing and that's OK... as I am one of the few and you are apparently one of the many.

The proper system for the proper application is always the objective when helping a customer solve their water treatment problems and concerns. A twin tank system is not always the proper application. For this application a twin tank system is the most efficient as stated by the numbers. Condescending comments are unprofessional and unfair to the customers we are trying to assist in this forum and only serve to confuse customers further.
RJ

RJ,

With respect, I am not trying to assist a customer and that may be where our differences lye. I am trying, and I believe succeeded, to educate the OP so he can help himself.

I believe the OP understands all that he's read in this thread and understands why a 2.5 cu ft softener with an SFR of 18 gpm is a wiser choice in his circumstances than a Fleck 9100 with 1.5 cubes in each tank.

People on these forums can recognize salespeople when they read them and since the OP is NOT a customer to me I have no dog in this fight other than posting accurate info for the benefit of all who read it.

If you took my remarks as condescending they were not intended to be. As far as unprofessional... posting numbers and not backing them up is unprofessional IMO. I'm still waiting for your answer on that imaginary 6000 grains per pound number you accused me of and have been avoiding explaining since you posted it.

I stand corrected on 6000gpp. At 6# per ft3 that is 5000gpp. I also stand corrected on the 195 gallons per regeneration it is 190 gallons.

Lets size the 2.5 ft3 softener for this application.
75 capacity - 6600 grains (1 day reserve) = 68400 grains.
68400 divide 6600 = 10.4 days
46200 divide 3080gpp = 15#na 52x15=782#na 52x190=9880 gal
68400 divide 3080gpp = 22#na 35x22=772#na 35x190=6650 gal
68400 divide 3500gpp = 20#na 35x20=702#na "
68400 divide 4000gpp = 17#na 35x17=597#na "

It would be helpful to reference the word condescending in wikipedia.
RJ