# Lowest salt dosage vs cost savings

Discussion in 'Water Softener Forum, Questions and Answers' started by Jason Ryan, Jun 18, 2018.

1. ### Jason RyanNew Member

Joined:
Jun 18, 2018
Location:
indiana
Hi all,

I've been crunching numbers trying to decide on a 48k or 64k system. My household is pulling ~10k gallons a month and our hardness is 23 according to our water company with very low iron and magnesium. I can pick up a great deal on a 48k system right now so that is definitely part of my decision (save \$250 vs 64k).

I've been trying to calculate the estimated salt cost for the different efficiency levels of both systems. What I'm having trouble figuring out is that according to my numbers, the most efficient usage of salt would be to go all the way down to a 32k system and run a 4lb salt dosage and just regen every couple days.

I'm sure that I have a calculation mistake, but what is the drawback of running the lowest possible dosage? My water costs \$0.44 per 101 gallons so it seems that even when I consider water cost (@ 50 gallons / regen), a 32k system at 4lbs seems the most cost efficient. Maybe the efficiency needs to consider the life of the resin and lots of regens might be bad...

BTW this forum is fantastic, and I've appreciated reading and learning so much on here over the years.

Thanks!

2. ### Reach4Well-Known Member

Joined:
Sep 25, 2013
Location:
IL
Do you have 6 or more people, or are you doing a lot of outdoor water use (which does not get softened).

Even a 2 cubic ft softener is undersized for you. At 6 lb/cuft, 2 cubic ft of resin softens 40000 grains or less. Don't use "64000" in a calculation. That number in practice is only code for 2 cuft of resin.

Here is the deal. Every night, typically 2 AM, a single tank softener checks to see if there is enough capacity remaining to make it through the next 24 hours. If there is not, it regenerates. On average, you will leave about 1/2 day of capacity unused. If you regenerate every 7 days, that 1/2 is not much loss. If you regenerate every 2 or 3 days, that is significant.

A twin tank softener does not have that limitation. It adds some complexity, but it can squeeze all of the capacity each time.

The downside of 4 lb/cuft is hardness leakage. 6 to 8 is the sweet spot for nice water and reasonable salt use.

Matt Peiris likes this.

Matt Peiris likes this.
4. ### Jason RyanNew Member

Joined:
Jun 18, 2018
Location:
indiana
Great explanation of the regen process. That explains a lot. I was never planning to use a system at max capacity (although we use up our existing 32k system regularly now). For the 48 or 64k system, I was thinking of a 6lb dose, but noticed the numbers were better for 4lbs. Thanks again for pointing out how the 2AM check point is a big deal though.

Regarding our water usage, we tend to have a lot of guest every few weeks. Looking at my water bill, I see that 3 months this year have been around 10k, the other months have been around 85k the lowest other month was 79k. My household is only 4 people, but I have two teenagers, a wife, and an on-demand water heater which is probably a recipe for disaster on water usage.

With the kids heading off to college in the years to come, I'm not sure I need to completely capacitize for the current spike. My home is 2.5 baths so nothing extraordinary.

5. ### Reach4Well-Known Member

Joined:
Sep 25, 2013
Location:
IL
2.5 cuft in a 13" x 54" tank is as small as I would consider for you. At 6 lb/cuft, that gives you 50000 grains of softening. That is called "80,000 grains" for advertising comparison use only.

Maybe trigger an early regeneration just before the extra guests arrive. That takes care of the worry of running out of soft water due to the extra use.

If you keep toilet plunger handy, it is probably time to consider getting a new toilet. The new ones tend to clog less, despite using less water.

6. ### ditttoheadWater systems designer, R&D

Joined:
Jan 9, 2012
Occupation:
Water systems designer, R&D, Technical Director
Location:
Ontario California
Here is a simple article explaining efficiency vs. quality. The vast majority of our customers use a 8 pound per ft3 dosage and they strive for 14 days between regeneration. Anything less than 7 days between regens will start to get very inefficient. Anything more than 14 is good, but the efficiency gains are negligible. https://view.publitas.com/impact-water-products/2018-catalog-final/page/66-67

7. ### Jason RyanNew Member

Joined:
Jun 18, 2018
Location:
indiana
Great article, thank you!

Looks like an 80k system with the 13" tank would push me to a 7000sxt type valve. Are there good sites to pickup components for a DIY build? If I were to look to buy the components locally, would any plumbing stores be the place to start (assuming I can get past the contractor license restrictions for some)? Thanks again!

8. ### Reach4Well-Known Member

Joined:
Sep 25, 2013
Location:
IL
5800 or 5810 valve would probably be a better choice. Click Inbox.