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Thread: Water softener sizing - what do I need?

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    DIY Junior Member opto_isolator's Avatar
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    Question Water softener sizing - what do I need?

    Building a new house, bought a Hach hardness and iron test kit. No iron detected in the water, hardness shows 8 gpg. The house has 3 full baths, right now it's just my wife and I, but will have guests visiting every once in a while, and a kid in the next year or two. I've tried reading and understanding the various sizing web sites, but am not sure what size I need. I've read that most companies size based on "size" versus cu ft of resin. Others say that I need to calculate my SFR, and go from there - but doesn't give any method to calculate the SFR. I'd like to get a Fleck 7000 series, as I think this will fit the bill for the size of our house, but not sure of how much resin / size I need. Can anyone help?

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    DIY Junior Member opto_isolator's Avatar
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    From what I'm reading - it sounds as if it may be good to go with a 1 cu ft resin softener, regenerating at 5-6 lbs of salt a week. This would provide reserve capacity for when it's needed - right?

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    DIY Senior Member mialynette2003's Avatar
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    The SFR is important if you are going to run ALL your faucets at the same time. When I say ALL, I mean every single water connection in the house. Most folks don't do this but may have a shower, washer and the dish washer going at the same time. So to size your unit, I would go by the days between regens. A 1 CF system set using the best salt efficiency will yield 20K @ 6 lbs of salt. So 20K/8GPG/2PPL/65Avg usage=19 days between regen. With a 1 day reserve, you will regen every 18 days. This is not bad unless the iron content is high which you said was not showing up. I take it that you are on well water?

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    That's all folks! Gary Slusser's Avatar
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    And a 1.0 cuft has a constant SFR of 9 gpm and when that is exceeded, the resin will not get your hardness down to 0 gpg. IOWs you get some hardness through the softener. IMO that's like buying a vehicle that won't start a couple times a week. Most shower heads are 2.5 gpm, faucets 2.0-2.5 gpm, washing machines 3-3.5 gpm, toilets 1-1.5 gpm.
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

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    DIY Junior Member opto_isolator's Avatar
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    Quote Originally Posted by Gary Slusser View Post
    And a 1.0 cuft has a constant SFR of 9 gpm and when that is exceeded, the resin will not get your hardness down to 0 gpg. IOWs you get some hardness through the softener. IMO that's like buying a vehicle that won't start a couple times a week. Most shower heads are 2.5 gpm, faucets 2.0-2.5 gpm, washing machines 3-3.5 gpm, toilets 1-1.5 gpm.
    So you recommend .75 cu feet?

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    DIY Senior Member Reach4's Avatar
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    Quote Originally Posted by opto_isolator View Post
    So you recommend .75 cu feet?
    I am confident that is not what Gary was saying.

    Click on the "Click Here" in Gary's signature. Follow that as best you can. Then click the link at the bottom of that page that will get you to a special calculator.

    You are unlikely to open every faucet at the same time. Having some hardness get by occasionally is not so bad. I expect that you have neighbors that have no softener at all.

    Most controllers allow you to set up a regeneration every week (although mine is not one of them). Many allow you to regenerate when you have used up enough capacity that you may exceed capacity by waiting a day, but set a maximum time between recharges that will occur even if you have not used any softened water at all.
    Last edited by Reach4; 12-20-2013 at 08:44 AM.

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    That's all folks! Gary Slusser's Avatar
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    If you use the entire capacity, which means you must set the salt dose at 15 lbs per cuft of resin you get 2000 grains of softening per lb of salt used, that's 30K in a 1.0 cuft (30,000 divided by 15= 2000). Compared to setting the salt dose to 6 lbs and getting 20K which is 3333 grains of softening per cuft of resin. That's an increase in salt efficiency of 1333 grains per lb. for every regeneration. I.E. if you went to a 1.5 cuft, at 6 lbs/cuft which is 9 lbs, you regenerate 30K where with a 1.0 cuft you need 15 lbs, or 6 more lbs for the same 30K of capacity. Plus, you never want to use all the capacity or you have to use 15 lbs per cuft to get all the resin regenerated again. It's like waiting to buy gas until you run out, it is not good to do that and can cause engine damage.

    Can you tell me how you got .75 ft out of what I said about SFR?

    Let's say you have 2 showers running (5gpm) and a toilet is flushed (1.5gpm) and someone starts the laundry washer (3.5gpm), your peak demand is the total of whatever is running so 10 gpm in my example. You would overrun the 1.0 cuft 9 gpm and not get all the hardness out of the water. And I'd be telling you that you should have bought a 1.5 cuft (12 gpm SFR) and set the capacity to the same as the 1.0 cuft and the salt to whatever lbs at 3333 grains per lb.. 2*60gals/day/person= 120* 8= 960* 8 days = 8640 rounded to 9K. That would be 1125 gals minus one day of 120 gals for the reserve with a meter setting of 1000 gals. 9000/ 3333= 3 lbs of salt per regeneration and that gets you a regeneration on average every 8 days with a constant SFR of 12 gpm. Then if you have a child, redo the math with 3 people at 60 gals per person etc..
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

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    DIY Junior Member opto_isolator's Avatar
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    Quote Originally Posted by mialynette2003 View Post
    The SFR is important if you are going to run ALL your faucets at the same time. When I say ALL, I mean every single water connection in the house. Most folks don't do this but may have a shower, washer and the dish washer going at the same time. So to size your unit, I would go by the days between regens. A 1 CF system set using the best salt efficiency will yield 20K @ 6 lbs of salt. So 20K/8GPG/2PPL/65Avg usage=19 days between regen. With a 1 day reserve, you will regen every 18 days. This is not bad unless the iron content is high which you said was not showing up. I take it that you are on well water?
    Thanks for the reply! I'm actually on city water (Florida). With regards to the regen - is there any way to set the regen to once a week? I know that it would be less efficient since wouldn't be using the entire capacity of the 1 cu ft of resin. Would it cause any harm to do this? I've read that if you wait too long to regen, the resin could get channeling or have other issues.

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    DIY Senior Member mialynette2003's Avatar
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    The chances of your unit channeling is slim to none. This would be more of a problem on larger units. Most of the electronic valve thses days have a day override. So if you set the day override for every 7 days, the system will regen if the gallon count has not reached it's max.

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