Water Softener Sizing

[acicomp]

Hey Folks,
I am new to the softener world and trying to come up to speed pretty quick. I have been doing a lot of reading through the forum, etc... Anyways... We bought the house we are in last year and the water hardness has consistently measured 15 gpg. I am preparing to purchase a new softener, most likely a Fleck 5600sxt and just wanted to get some opinion on the correct size for efficiency.

We have the following to go by:
7 people in the house (Hopefully to drop lower in the next year or two as some finish college...)
2 Bathrooms
Hardness - 15gpg
Well Water with sediment filter after well pump
No iron issues
3/4 piping

I was originally, at a glance, thinking about a 5600sxt - 48,000 grain, however, before I purchase, after looking at the calculator I saw here on the forum tonight, I might be better off with the 5600sxt - 64,000.

Can someone give some insight here to what the more efficient size would be to help keep salt purchases to a minimum down the road?

Thanks for any input!

 

[ditttohead]

The larger system would be better, up to a certain size, larger will be more efficient. If you go past 30 days between regenerations, the larger sizes are wasted.

 

[Sponsor]

 

[acicomp]

The Fleck 64K Setup I am looking at has 2 Cubic feet of resin. Based on this, I think I have calculated the settings here for both the 6lb and 8lb salt usage. The 6lb setting would be approximately 12lbs per regeneration and the 8lb setting would be approximately 16lbs per regeneration. I would still go with the 64k unit to allow for some overhead if we had guests or missed a regeneration due to usage. I know there is a little tradeoff between the 6lb and 8lb. The 6lb setting obviously uses less salt, but possibly a little more water from what I understand. The 8lb setting used slightly more salt, but uses a little less water from I understand. I have used both 60 and 75 gallons per day as calculations for our family of 7. I know there are some other variables that might cause this to vary some, but I’m still in the basic learning mode.

7 People x 60 Gallons x 15gpg = 6300 Grains

7 Day Regeneration = 44100 Grains (8lb Setup @ 48K) x 52 regenerations = 832lbs = 21 bags x $6 per bag = $126 per year

6 day Regeneration = 37800 Grains (6lb Setup @ 40K) x 61 regenerations = 732lbs = 19 bags x $6 per bag = $114 per year

7 people x 75 Gallons x 15gpg = 7875 Grains

6 Day Regeneration = 47250 Grains (8lb Setup @ 48K) x 61 regenerations = 976lbs = 25 bags x $6 per bag = $150 per year

5 Day Regeneration = 39375 Grains (6lb Setup @ 40K) x 73 regenerations = 876lbs = 22 bags x $6 per bag = $132 per year

Thanks for the input!

 

[Bannerman]

While you're on the right track, there is an alternate method to compare efficiency.

A 1 cuft softener, although typically rated as having 32K grains capacity, is generally considered to realistically have a total capacity of 30K as some capacity will be lost over time. To regenerate all 30K would require 15 lbs of salt, therefore providing a salt efficiency of 2K grains per pound.

If the same unit is programmed to regenerate using 10 lbs/salt, then 27K grains capacity can be restored which results in 2,700 grains per pound salt efficiency.
An 8 lb setting can restore 24K giving an efficiency of 3K/lb.
A 6 lb salt setting will restore 20K at an efficiency of 3,333 grains/lb.

The capacity and salt settings applicable for a 2 cuft unit are 2X those stated above, to obtain equal salt efficiency.

As your requirements are fairly high due to the number of residents, you would want a softener sized to satisfy your requirements while not requiring more than a weekly regeneration. You could utilize a slightly less efficient setting initially and then make adjustments latter to increase efficiency as some of the residents leave the nest, OR, utilize a larger softener programmed at the most efficient setting right from the start.

As you specified, your daily requirements are currently 6300 grains (60 gallons/day is typically found to be the current average consumption), then your weekly requirements would be 44,100 grains. A 2 cuft programmed with a 6 lb/cuft setting, would not deliver your weekly needs whereas an 8 lb/cuft salt setting would deliver just enough at 48K. (7.6 (7 day) regeneration cycle)

A 2 cuft using a 10 lb/cuft setting will provide 54K usable capacity so the regeneration frequency would then be 8.5 (8 days) initially, since you also mentioned concern with water consumption. A softener will typically utilize ~75 gallons of raw water (not softened) to regenerate.

A 2.5 cuft unit will provide 60K capacity with an 8 lb/cuft setting, thereby extending the regeneration frequency to 9.5 (9 days) at 3K per lb. The same 2.5 cuft unit would deliver 50K with a 6 lb/cuft setting thereby needing a 7.9 (7 day) regeneration frequency. As members of your home leave the nest and less water is utilized, the regeneration frequency will become less. As Dittohead mentioned, the regeneration frequency should not be longer than 30 days.

As I expect the eventuality will be 2 people remaining in the home, the requirements will then be 1800 grains/day. A 2 cuft softener would then require regeneration (40K / 1800) = 22 days when using a 6 lb salt setting whereas a 2.5 cuft unit would be 27 days.

 

[acicomp]

If I used a 80K softener (2.5 Cu. Feet), this is what I calculate for an estimated yearly usage. These are rough numbers, but anyways...

7 Day Regeneration = 44100 Grains (6lb Setup @ 50K) x 52 Regenerations = 780lbs = 20 bags x $6 per bag = $120 per year
9 Day Regeneration = 56700 Grains (8lb Setup @ 60K) x 41 Regenerations = 820lbs = 21 bags x $6 per bag = $126 per year

It seems like the overall usage of salt, which is the primary concern since I am on a well and don't pay for water, would be "almost" as efficient using a 64K unit (2.0 Cu. Ft.) as it would be the 80k unit (2.5 Cu. Ft.)

Long-term, I could see that adding 5 days to the regeneration would, at a first glance, seems a little better if it ever gets down to just my wife and myself. But I am one of those people that wonder where the break even takes place on the investment. On a 6lb setup, it ends up that the 64k unit (2.0) @ 17 Regenerations per year = 204lbs of salt per year and the 80k unit (2.5) @ 14 Regenerations per year = 210lbs per year. If the unit lasts 20 years, we would save $18 over the lifespan by going with the 64K unit. Also, if we always had 7 in the house, even if kids move out and the future grandkids (100 years from now... Ha!) are over here, the 64K unit (2.0) @ 732lbs vs the 80K unit (2.5) @ 780lbs would possibly save us $144 over 20 years.

All the numbers are starting to swirl in my mind, so please let me know if I have missed something here. It seems like the 64K unit would be the best selection for us here. I know all these numbers are fairly generic and rounded and there are always other variables like actual water usage, etc...

Thanks for all the help!