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Water Softener Sizing Help

Posted by smithb39 (My Page) on
Thu, Jul 14, 11 at 7:27

I was wondering if I could get help with sizing a water softener. Recently, the last yr we had an old timer based softener quit on us, I had a local Kinetico dealer come out and test our water, they suggested the model 2060 for our needs. I was thinking of installing a Fleck based softener, but wanted a second option on what size I would need.

- Family of 5 (2 adults, 3 kids: 5yr, 3yr, 2yr old)
- Small house 1000 sqft, 3 bedrooms, currently remodeling basement which will add a second kitchen sink to make total sqft of 1500.
- Two washing machines (2nd used for washing hunting clothing in the fall)
- Dishwasher
- 2 baths (1 standing shower, 1 standard tube), nothing fancy just one shower head in each bath
- No jacuzzies, hot tubes, or any additional large water uses.

- I have city water
- 3/4 inch copper water inlet
- Hardness=29 GPG
- Iron=0
- PH=7.25
- Dissolved Solids: 611 PPM
- Chlorine=None Detected
Using a calculation of 60 GPD per person.

5 people x 60 gallons/day x 29 grains hardness = 8700 grains per day x 7days = 60900 Total Grains of Capacity

What I'm having trouble is trying to determine the softener size in cu ft based on the idea of 6 lbs/cu ft. I think it would make it a 3.0 or 3.5 cu ft softener? Based on that size I would need a Fleck 7000SXT if I'm not mistaken. Also with 2 adults and 3 children, I wonder if factoring in 5 people for 60 gallons/day might be overkill until they grow older.

Any help would be appreciated.

Follow-Up Postings:

RE: Water Softener Sizing Help

3.5 cu ft softener set up @ 64k capacity @ 5 lbs salt / cu ft of resin (18 lbs total salt dose for 3.5 cu ft) will regenerate every 7 days or so.

Set calendar override for 8 days.

Fleck 7000 is a good choice.

Make sure you get a gravel under bed... regardless of what the softener salesman says.

RE: Water Softener Sizing Help

3.5 cu ft softener on a 3/4" water line?

Wouldn't bed channeling be an issue on a 8 day cycle with such low flow probabilities?

RE: Water Softener Sizing Help

Shouldn't be with 5 people in the house and the gravel under bed will help. Even though the kids are small they make up for their size in washer loads. As the kids get older the water use will rise. The 3.5 cube unit requires a minimum 4 gpm backwash flow rate.

You could go down to a 3 cu ft unit @ 64k @ 7 lbs salt / cube (21 lbs total dose per regen). Not as efficient as the 3.5 cube.

RE: Water Softener Sizing Help

Your right about the wash loads, with the kids being all boys, it seems like something needs cleaning all the time.

Thanks for the help, I'll let you know what I get an how it works out.

RE: Water Softener Sizing Help

I might suggest a twin-tank design. It will eliminate the guessing and give continuous treated water during high and low usage equally.

RE: Water Softener Sizing Help

A twin resin tank softener will be a compromise with a lower SFR when each smaller tank is in service. With 5 people using water in different areas of the home that's not a good compromise... especially as they get older.

RE: Water Softener Sizing Help

A twin tank fleck 9100 with 1.5 cu ft of resin per tank will work just fine. 14 lb salt dose and you will have a system that will last for 20+ years and will adjust to your changing water usage with no chance of channeling.

RE: Water Softener Sizing Help

"A twin tank fleck 9100 with 1.5 cu ft of resin per tank will work just fine. 14 lb salt dose and you will have a system that will last for 20+ years..."

And in that 20(?) years that undersized 1.5 cube twin 9100 softener will regenerate every 3-4 days using over twice the salt in a week as a correctly sized softener, running more water to drain in a week during regeneration than a correctly sized softener, and with a far lower SFR than a correctly sized softener.

With the reduced SFR of 1.5 cu ft during peak water usa hardness will leak through. If one is paying for soft water they ought to get it.

There is a time and a place for a twin but with these water conditions and occupancy this is not the place for a 1.5 cube (each tank) twin.

RE: Water Softener Sizing Help

I agree with rjh20. A 1.5 x 2 twin would work PERFECTLY. The whole SRF philosophy is so over rated and only with extreme rarity would this become an issue unless you are using water in a commercial setting.

I have been dealing with twin-tank systems for nearly a decade and have never had any reported issues of flow rate or hardness leakage due to too many using water at the same time. With your settings, smith39, you would have to actually try very hard to cause flow issues. BTW, what size plumbing do you have, 3/4"?

Furthermore, I would never imagine putting a monstrosity of a 3.0 cuft (14x60) water softener on only 29 grains of water. I often use a twin of no more than 8x48 tanks and they work perfectly even with a family more than five.

Smith39, you will not have any issues with flow problems or hardness leakage. There are many other advantages of using a twin-tank system but that have been mentioned elsewhere.

RE: Water Softener Sizing Help

"The whole SRF philosophy is so over rated and only with extreme rarity would this become an issue unless you are using water in a commercial setting".

So overrated that code requires SFR be carefully calculated for plumbing, appliance, and fixture requirements.

With 5 people in a house with 29 gpg water the "extreme rarity" of exceeding SFR can be a common occurrence and the fact that homeowners don't know that hardness is leaking through doesn't make under sizing a softener ethically or technically correct.

In reality many undersized softeners are sold everyday because too many softener sales people have too cavalier an attitude towards correct sizing to keep the cost to the consumer as low as possible or are in the business of selling small softeners that regenerate more frequently and just ignore SFR requirements.

Doing something the same way for decades doesn't make it right when it's wrong.

RE: Water Softener Sizing Help

Oh JAL do we really need to have this argument again just because you are fixated on 2+cu ft softeners and having to regenerate every 7 days. There is a huge difference between
SFR (service flow rate) and PFR (peak flow rate). The twin tank system Andy & I recommend will give plenty of SFR and a peak flow rate of 12 gpm (which happens seldom).
Your recommendations will cause hard water channeling at low SFR. Where did 5lbs salt dose come from? 6lbs per cu ft is the standard for efficiency so lets apply this properly and compare the correct values. As per discussions previously a twin tank is not for every application but in this instance it is the perfect for this application and family.

RE: Water Softener Sizing Help

We will continue to have this disagreement as long as you continue to recommend undersized softeners.

I'm fixated on the math and the physics and what they tell me.

6 lbs / cu ft of salt... who's standard? There is no documentation I'm aware of that precludes using 5 lbs / cu ft in the right circumstance.

You under size softeners and I short-salt resin... and at 5 lbs / cu ft of salt the numbers work.

We can agree to disagree.

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