# Properly Sizing a Water Softener



## zerious (May 3, 2012)

Hi, I'm new to the board and hope this is the correct place to post a new thread about water softener sizing. 

I'm hoping Gary Slusser is available to add his expertise.

The system needed would be for a family of 3 adults + one adult away at school. 

There are 3 bedrooms, 2 full baths and 2 half baths. The master bath includes a shower with rain type head, no body sprays, and a 50 gallon spa tub which draws 3.5 gpm (did the 5 gal. bucket test 3x) the tub and shower are not used at the same time. 

The professional water test had these results :

[FONT=Arial, Helvetica, sans-serif]Well Water :

Coliform : absent
Chlorine : absent
Hardness : 111 mg/L (6.49 gpg)
Manganese : ND
Iron : 0.01 mg/L
PH : 6.7 SU
Turbidity : 0.2 NTU[/FONT]

[FONT=Arial, Helvetica, sans-serif]Avg daily water useage per adult has been 70 gpm.
The gpm at the pressure tank ranges between 11.5 to 14 depending on pump activity.

[/FONT][FONT=Arial, Helvetica, sans-serif]I've done quite a bit of research on sizing a system and am still at a loss as to how to best determine the Service Flow Rate of standard resin in respect to the different Service Flow Rates (maximum, constant, peak, etc.) at the site, in order to calculate how much resin would be required to be most efficient.

I've spoken to four local dealers and their opinions all differed extremely, from a 1.0 cu. ft. system to a 2.5, even though I gave them all the same operating parameters. [/FONT]
[FONT=Arial, Helvetica, sans-serif] 
I would appreciate any insight on choosing the correct size unit and any suggestions on other sites to post this question.

Thank you, Fritz[/FONT]


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## joecaption (Nov 30, 2011)

This may or may not help.
http://www.qualitywatertreatment.com/water_softener_sizing.htm


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## zerious (May 3, 2012)

Thanks for responding with the link. I have been to the site many times and do not comprehend how to calculate the misc. SFR's which are required to properly evaluate the capacity of the resin for most efficient and effective salt usage. I'll keep trying to learn more.

Have a good day


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## a7ecorsair (Jun 1, 2010)

zerious said:


> [FONT=Arial, Helvetica, sans-serif]Avg daily water useage per adult has been 70 gpm.
> The gpm at the pressure tank ranges between 11.5 to 14 depending on pump activity.
> [/FONT][FONT=Arial, Helvetica, sans-serif][/FONT]


I doubt you are using 70 gallons per minute.
Your grains of hardness aren't that high.
What are you concerned about, how often the system will regenerate?


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## a7ecorsair (Jun 1, 2010)

This is the calculations from the site. For a approximate 7 day recharge you can use a 24000 grain unit.


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## Bob999 (Mar 4, 2010)

a7ecorsair said:


> This is the calculations from the site. For a approximate 7 day recharge you can use a 24000 grain unit.


 With iron of .01 mg/l the appropriate entry in the calculator for iron is .01.


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## a7ecorsair (Jun 1, 2010)

Bob999 said:


> With iron of .01 mg/l the appropriate entry in the calculator for iron is .01.


Ya, .01 is negligible so I stuck in 2.0 just for a margin. The chart doesn't allow less than 1.0. Same answer.
If you use one of the water softeners that recharges based on usage and not on a fixed time, all you do is tell it you grains of hardness.
If the OP is worried about capacity, he could just install an automatic 32000 grain unit and not worry.....


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## zerious (May 3, 2012)

Thanks for the responses. 

Sorry, I meant 70 gpd/pp not 70 gpm.

I used the calculator for 4 people with 7 gpg + 1 gpg and came up with 3000 gpd to be removed which says I need a 24K grain capacity softener. 
If I wanted a more efficient use of salt, say in the 5 to 6lb. range, wouldn't I need more resin capacity, like 1.5 cu.ft.? 
I also want to make sure to have a higher flow rate capacity than a 24K's resin bed could soften. Would a 48K system be too large? 

From the research I've done, my understanding is that I may need the capacity of the resin to handle a flow rate of at least 12 gpm for those times that the spa tub may be filling, the dishwasher is running and someone flushes a toilet or uses a faucet. My understanding is that I need 1.5 cu.ft. of regular resin to get 12 gpm. 

Sorry to ask so many questions and hopefully I have phrased them correctly.


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## Bob999 (Mar 4, 2010)

If you have copper plumbing you should treat the mild acidity of your water--otherwise you will have pin hole leaks develop in time as well as elevated levels of copper in your water supply. The most common method of treating acidity is an Acid Neutralizing filter-a backwashing filter similar to a softener except the media is calcite and there is no regeneration--only backwashing to clean and reclassify the media. Calcite media is sacrificial in acidic water and is periodically refilled. A calcite AN filter will raise the pH a bit--probably to about 8 grains/gallon in your case and would have little affect on the softener sizing decision.

As to the size of the softener--you didn't specifiy the gpm of the shower head--if it is 3 gpm or less I recommend a 1 cubic foot softener programmed to regenerate approximately once per week.


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## Bob999 (Mar 4, 2010)

zerious said:


> Thanks for the responses.
> 
> Sorry, I meant 70 gpd/pp not 70 gpm.
> 
> ...


1. Why are you using 4 people for sizing if one is not residing in the home? It seems to me that the calculation would be 3 people at 70 gallons/day at either 7 or 8 grains/gallon gives a daily load of ~1500 grains to ~1700 grains or ~11K to ~12K grains per week. Even with a 4th person--an increase of 1/3 the weekly load would be ~16K which can be achieved efficiently with a 1 cubic foot softener.

2. A 1 cubic foot softener is fully effective up to 9 gpm. Leakage will increase above 9 gpm but only gradually. You posted the spa tub fills at 3.5 gpm. A diswasher fills at less than 2 gpm. A toilet fill rate is adjustable with most models but 3-4 gpm for an modern toilet is a reasonable estimate. These three items total less about 9 gpm--well within the capabilities of a 1 cubic foot softener.

3. There are cons to oversizing--cost, need to use very low salt dose to do the recommended weekly regeneration with resulting higher leakage rates, and potential for channeling in extreme cases.


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## zerious (May 3, 2012)

a7ecorsair said:


> Ya, .01 is negligible so I stuck in 2.0 just for a margin. The chart doesn't allow less than 1.0. Same answer.
> If you use one of the water softeners that recharges based on usage and not on a fixed time, all you do is tell it you grains of hardness.
> If the OP is worried about capacity, he could just install an automatic 32000 grain unit and not worry.....


Yes I am planning on using a meter? control valve based on usage. I was thinking of the Fleck 5600 SXT. Fleck 2510 SXT, or the CS1 EE. Just don't know if the 5600 flow rate is enough if I go with the 48K system.

I am looking at a couple of the systems available at the QWT site. Is anyone familiar with the CS1 EE? If I don't go with the 5600, I'll need to decide between the 2510 and the CS1. I am also trying to decide if upgrading to the SST-60 resin is cost effective and will give the system better performance.


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## Bob999 (Mar 4, 2010)

SST-60 is typically used in high iron situations--you do no have iron. SST-60 will give slightly better salt efficiency IF you know how to properly program the unit--and you do it. The slight increase in salt efficience won't pay for the increased cost of the resin. In other words it is not a cost effective choice in your situation.

The "CS1 EE" valve is, I believe, a Fleck valve--same brand but different model as the other two you are looking at. Check here:
http://www.pentairwatertreatment.com/en-us/Products/ResidentialControlValves/Fleck+6700XTR.htm

Fleck makes good valves and any one of the valves you are looking at should provide good service.


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## zerious (May 3, 2012)

Bob999 said:


> 1. Why are you using 4 people for sizing if one is not residing in the home? It seems to me that the calculation would be 3 people at 70 gallons/day at either 7 or 8 grains/gallon gives a daily load of ~1500 grains to ~1700 grains or ~11K to ~12K grains per week. Even with a 4th person--an increase of 1/3 the weekly load would be ~16K which can be achieved efficiently with a 1 cubic foot softener.
> 
> 2. A 1 cubic foot softener is fully effective up to 9 gpm. Leakage will increase above 9 gpm but only gradually. You posted the spa tub fills at 3.5 gpm. A diswasher fills at less than 2 gpm. A toilet fill rate is adjustable with most models but 3-4 gpm for an modern toilet is a reasonable estimate. These three items total less about 9 gpm--well within the capabilities of a 1 cubic foot softener.
> 
> 3. There are cons to oversizing--cost, need to use very low salt dose to do the recommended weekly regeneration with resulting higher leakage rates, and potential for channeling in extreme cases.


1. I would prefer to rate it for 4 because college kids are home sometimes especially in the summer. The spa tub may only be filling at 3.5 gpm because of the existing 15 year old 24K cabinet style softener. Also, I forgot to mention a rain shower head is sometimes used in the shower, it has it's own valve and I think it would be used more often if it had a better flow.

2. Add in a faucet and we're well over 9 gpm. Plus the rain shower head I forgot about, although it would not be used at the same time as filling the spa tub.

3. Thanks for pointing out the cons. I understand about the potential for channeling. One of the valves I am considering has an automatic override for low water usage so you can tell it to regen at say 7/8 days even though the usage does not initiate a regen. Is a 5-6lb salt dosage considered low? Why could there be higher leakage rates? Would it be because there is not enough brine with a lower salt setting to regen the resin effectively?

I really appreciate the input. I certainly don't want to oversize or undersize the system. The cost of a larger unit seems minimal if the salt and water used to regen will be similar for both the smaller and larger units. Wouldn't the larger unit also allow for less frequent addition of salt to the brine tank, and also allow for a better peak service flow so no hardness breaks through?


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## Bob999 (Mar 4, 2010)

When I post about "leakage" I am referring to hardness leakage.

On one hand you seem concerned about salt efficiency. And then you seem to abandon salt efficiency when you talk about automatic override (a setting in some electronic softener valves that allows the unit to be programmed to regenerate after "x" days even if the metered usage does not indicate regeneration is necessary.

As I tried to point out above a 1 cubic foot unit will flow more than 9 gpm but hardness leakage will increase a bit at higher flow rates. For typical residential applications this is not a problem.

One of the advantages of SST-60 resin is that its hardness leakage is better than standard "high capacity" resin at low salt dose.

Generally anything less than 6 lbs/cubic foot would be considered low salt dose and I don't recommend going below 4 lb/cubic foot with standard resin. With SST-60 comparable leakage performance can be maintained below 3 lb/cubic foot.

With a demand control head occasional higher usage is taken care of with more frequent regeneration--you don't need to size the unit basic on occasional occupancy.

The need to add salt to the brine tank is determined by the size of the brine tank, the hardness removed, and salt efficiency. It has only an indirect relationship to the amount of resin. Personally I recommend adding salt one bag at a time because it is appropriate to regularly check for proper operation and it is a lot easer to remove a couple bags of salt if repair is necessary than to remove a couple hundred lbs!


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## zerious (May 3, 2012)

Bob999 said:


> SST-60 is typically used in high iron situations--you do no have iron. SST-60 will give slightly better salt efficiency IF you know how to properly program the unit--and you do it. The slight increase in salt efficience won't pay for the increased cost of the resin. In other words it is not a cost effective choice in your situation.
> 
> The "CS1 EE" valve is, I believe, a Fleck valve--same brand but different model as the other two you are looking at. Check here:
> http://www.pentairwatertreatment.com/en-us/Products/ResidentialControlValves/Fleck+6700XTR.htm
> ...


Thank you for the link to the pentair site. I think you are correct about the CS1 being a Fleck. I still need to decide on which Fleck valve, guess I'll be doing some reading and research. Thank you also for your opinion on the cost effectiveness of the SST-60, I was also looking at it as possibly having a better "in service" flow rating. Thanks for reminding me about learning to properly program the unit if I choose to go with SST. Do you happen to know if one of those Fleck valves would be better than another to use for programming with the SST resin?

Any opinion on using a noryl? versus a stainless bypass? I also read about adding an upper basket on the riser tube before attaching the valve. BTW thanks for the PH suggestion, no room to incorporate it, nor the funds to purchase it.

Thanks for all your time to answer my flood of questions. I really appreciate it.


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## Bob999 (Mar 4, 2010)

1. Proper programming is critical for good salt efficiency with any resin. Most suppliers ship valves programmed for maximum capacity and maximum salt dose which equals very low salt efficiency.
2. The SXT electronic version of the 5600 or the 2510 is fully programmable as is the 6700XTR. The important difference between the valves is the internal passage sizes which shows up in the spec sheets as flow rate for a given pressure drop. There are other differences but they really don't affect your application in my view.
3. I would lean toward the stainless bypass--and definitely chose it if using plastic to connect to it because you should use a male plastic fitting into a metal female fitting. (The stainless bypass is female.)


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## zerious (May 3, 2012)

Bob999 said:


> When I post about "leakage" I am referring to hardness leakage.
> 
> On one hand you seem concerned about salt efficiency. And then you seem to abandon salt efficiency when you talk about automatic override (a setting in some electronic softener valves that allows the unit to be programmed to regenerate after "x" days even if the metered usage does not indicate regeneration is necessary.
> 
> ...


Sorry for not explaining my scenario more clearly. Thank you for clarifying. I am starting to understand that I can go with a smaller sized unit, configured for 3 people, using a better resin for less hardness leakage, with a properly programmed demand control valve so that it will regenerate more often when there are more people, but may have occasional leakage when the Service Flow Rate is exceeded.

I am concerned about salt efficiency and now understand that I would be abandoning the salt efficiency by overriding the demand generated regeneration in order to avoid the potential for channeling in a system sized for more people when less water use occurred. 

Thanks for the suggestion on not filling the brine tank with an overabundance of salt. I understand how it could impact the ease of visually checking the brine level, float mechanism, etc.

This softener upgrade all started because I need to add an indirect hot water storage tank (which I am still researching) to the boiler because we don't get enough hot water from the tankless coil in it, which I think may be restricted by scale because of the existing softener. I had the water tested before and after the existing softener and the tests were nearly identical. So, I was trying to restrict if not completely eliminate hardness leakage, to extend the life of the new indirect, and was hoping I could have both salt efficiency and a unit with the proper amount of resin capacity to satisfy the service flow we need/want if it is configured and programmed correctly.

I am still concerned about a 1.0 cubic foot unit being adequate. But I need to start trusting your and others opinions because I certainly lack the knowledge and experience necessary to make this decision. I have spent way too much time reading and analyzing research online and have to get on with my life. So, I would prefer a unit that will not have any hardness leakage under normal operating circumstances (I am assuming this means a SFR adequate to provide +/- 12 gpm at peak usage), that is as salt efficient as possible. I would like it to use the 5 to 6 lbs/cubic foot ratio and for it to regenerate once every 7 to 8 days when 3 people are making use of the system. 

Thanks again.


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## Bob999 (Mar 4, 2010)

I think you are too focused on "hardness leakage". If you size a softener so that you are regenerating with about 6 lbs/cubic foot you will have VERY little leakage. So little that typical home tests won't detect it.


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## zerious (May 3, 2012)

Bob999 said:


> I think you are too focused on "hardness leakage". If you size a softener so that you are regenerating with about 6 lbs/cubic foot you will have VERY little leakage. So little that typical home tests won't detect it.


I spent some more time today reviewing the different Fleck valves and speaking with different dealers about their opinions on the Fleck 2510sxt versus the 5600sxt versus the 6700xtr. Basic differences I came up with are that the 2510 has 2 motors, may be more durable, but can be more difficult to repair, that the 5600 and 6700 are the same valve body with different computers, the 6700xtr can do variable brining, upflow regeneration, and can keep better statistics and is easy to repair. I will be going with the 5600 or 6700 depending on whether I need/want variable brining since I'll be going with the SST-60 resin. Don't think I want or need upflow regeneration because the SST-60 is already more efficient. Do you think the 6700 is beneficial in regards to its use with the SST-60 for variable brining? Is variable brining another way to tweak the salt dosage for efficiency? Or is this just complicating things.

I've pretty much given up on going with a 48K unit as per your advice.
I am trying to decide between a 32K and a 40K. I don't know why I can't just accept that a 32K unit is sufficient. I understand that a 32K with 1.0 cubic foot of resin at 6 lbs/cubic will take care of 20,000 grains of hardness and that the SFR will be 9 gpm. When I calculate my needs I come up with 4 people x 75 gpd = 300 x 8 gpg = 2400 x 8 days = 19,200 so, I can see that a 32K unit can handle the water usage. I was just wanting to give myself some more elbow room for the SFR. So if I look at a 40K system, I understand that it can take care of 25,000 grains at 6 lbs.
and will give me a SFR of 10 gpm. If I drop the salt dose down to 5 lbs. or 4 lbs. will this size system still be inefficient in your opinion?

Thank you Bob999, I'm almost there!


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## Bob999 (Mar 4, 2010)

I have no experience with variable brining--and in a quick look at the posted literature for the 6700 I didn't see any mention of variable brining. Unless you really understand how to program it or have someone you can turn to I would recommend staying away from variable brining.

You have previously posted that your normal house occupancy is 3 people--NOT 4-- and that your daily use averages 70 gal/person NOT 75 so I don't understand why you are not using 3 people and 70 gal/person in your calculations.

You posted "I understand that it can take care of 25,000 grains at 6 lbs." What you should have said is that "I understand that it can take care of 25,000 grains at 6 lbs/cubic foot or 7.5 lbs per regeneration".

So the problem with a 1.25 cubic foot unit is that your estimated 8 day grains/gallon is 8 gpg x 3 people x 70 gpd x 8 days = 13,440 grains and this puts the indicated salt dosage at about 2.5 lb/cubic foot with SST-60 resin. Even with a 1 cubic foot unit and SST-60 resin the indicated salt dose for 13,440 grains is about 3 lbs/cubic foot.


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## zerious (May 3, 2012)

Bob999 said:


> I have no experience with variable brining--and in a quick look at the posted literature for the 6700 I didn't see any mention of variable brining. Unless you really understand how to program it or have someone you can turn to I would recommend staying away from variable brining.
> 
> You have previously posted that your normal house occupancy is 3 people--NOT 4-- and that your daily use averages 70 gal/person NOT 75 so I don't understand why you are not using 3 people and 70 gal/person in your calculations.
> 
> ...


I read an article from Pentair and I now understand why the 6700xtr would be used for some systems. I also have a better comprehension of regeneration efficiency, downflow versus upflow brining, and variable brining. You've probably read this article but if not here is the link http://www.watertreatmentguide.com/achieving_brine_efficiency_in_softening.htm
I agree that 6700 would be overkill for my system because I don't want to deal with an upflow regeneration unit at this time. Even though it it shown to be more efficient I'd prefer to avoid the additional setup parameters required and to use the SST-60 instead because it is supposed to be almost as good in a co-current system as it is in a counter-current system.

Yes, I had previously posted that normally 3 people would be using 70 gpd each. I got this info from the existing softener's computer. I now understand your reasoning on why my calculations should be based on 3 people not 4. It is because I will be using a demand initiated control valve which will regenerate based on the water used, whether there are 3 or 4 people. The reason I changed the consumption value is because, I assume, that when the new softening system is in service and we have hot water lasting longer (because of a newly added indirect water heater), that usage will probably increase. I'm not saying that this is good, I'm just saying that it is probable.

I think I understand that even using a calculation based on 3 people at 75 gpd/pp, equaling 225 gpd x 8 gpg = 1800 grains per day x 8 days between regenerating = a 14,400 grain hardness removal capacity (don't know if I phrased that correctly), a 32K unit's 1.0 cubic foot of regular resin can effectively handle the removal of the projected 14,400 grains of hardness. Am I correct in assuming that 6 lbs. of salt will regenerate the 1.0 cubic foot of resin with up to 20,000 +/- grains of hardness attached to it? 

I don't understand what "indicated salt dosage" means. 
It seems to be in reference to the SST-60. If I understand this correctly, 6 lbs. of salt will regenerate 20,000 grains, so 13,440 grains would need 67.25% of the 6 lbs., 6 x 67.25% = 4.035 lbs to regenerate 1.0 cubic foot of regular resin with 13.440 grains of hardness. I'm not confident my calculations are correct because I don't understand the physics of regeneration and don't know if linear calculations can be used. I hope that I am basically calculating this correctly. If so then, would 14,400 grains need 72% of 6 lbs. or 4.32 lbs. of salt to regenerate 1.0 cubic foot of regular resin effectively? And even less of a salt dosage for SST-60? I could not locate the indicated salt dose for SST-60 at the Purolite site.

So, if I go with the 1 cubic foot unit using the SST-60 what would you personally like to see for a salt dose setting? Use the indicated? where? salt dose of 3 lbs/cubic foot? How often would this regenerate based on 13,440 grains? Or would using a higher salt dose setting with less efficiency be more effective?

I really appreciate your assistance and opinions. You've helped me to focus on the task at hand and I am starting to better understand the intricacies of properly sizing a system.


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## Bob999 (Mar 4, 2010)

Salt dose is not linear. To illustrate: 15 lbs/cubic foot yields ~ 30K and 6 lbs/cubic foot yields ~ 20K.

Salt dose for any given capacity is different for SST-60 as compared to standard resin.


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## cgarai (May 12, 2012)

*Salt dosage, leakage, controlling final hardness*

Hi, 

Perhaps this should be a new thread. Let me know and I'll re post it.

A couple of questions:

1. I am wondering how to adjust the final hardness of softened water. The reason for this is that I am installing a condensing water heater that requires that hardness be maintained between 5 and 7 gr/gal. I am starting with water that is 13 gr/gal. I have read that reducing the salt dosage allows the final hardness to be above 1 gr/gal, but it is not clear to me by how much.

2. I understand that SFR is 7gpm/cuft. (although I have seen references to it being non linear). How does one avoid channeling? Is there a minimum flow/cuft? I assume that channeling doesn't occur just because a low flow is being demanded over the short term (a single low flow tap on for 2 minutes). It must occur over a longer time if insufficient peak flow rates don't occur often enough. 

3. How does softening affect TDS? 

4. I have read much about salt dosage and brine efficiency, but I don't understand how to set it up. I don't see mention of salt dosage in the programming manuals for the 2510SXT, 5600SXT or 7000SXT. It is briefly mentioned in the 6700 Upflow manual. How is it set in these other controllers? Seems like I'm missing something.

5. I'm not too concerned about hardness leakage if SFR is exceeded on occasion. Why is it mentioned so much? I don't see a problem with occasional briefly elevated hardness or am I missing something (again)?

6. What is upflow brining? Is it more difficult or expensive? How much more brine efficient is it? Is it more water efficient?

7. My intention is to use one of the above Fleck valves. Any opinions about them? I am having a hard time finding a good comparison of the features and capabilities.

Thank you, 

Chris


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## Bob999 (Mar 4, 2010)

cgarai said:


> I am installing a condensing water heater that requires that hardness be maintained between 5 and 7 gr/gal.


What brand/model of condensing water heater requires this? Could you please provide a link to the literature that requires this?


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## cgarai (May 12, 2012)

Hi 

Heat Transfer Products is the manufacturer, Phoenix Solar is the specific product I will be installing. You can find the installation guide here:
http://www.htproducts.com/literature/lp-179.pdf
The reference is on p.15.


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## Bob999 (Mar 4, 2010)

1. To adjust hardness you must blend raw water and softened water to achieve the desired hardness. Adjusting salt dose is not a reliable way to control hardness--if you adjust the salt dose down you will get soft water (less than 1 grain/gal) for a while and then when the resin is exhaused the hardness will rise to that of the softened water. But with regard to the requirements in your installation manual note it say soft water MAY be under saturated... Do a search for the Langelier saturation index and do the computations to see what the index would be for your water if softened--you may not have a problem with soft water.

2. The service flow of a 1 cubic foot softener is typically described as 9 gallons. A properly sized and regularly regenerated softener won't have channeling problems.

3. Softening changes TDS very little-perhaps a very small increase.

If you provide a complete water analysis and the specific softener you have I can suggest salt efficient settings. If you provide family size, specifics of special fixtures like multihead showers and large tubs or anything else than would increase your overall water usage or typical flow rates I can suggest an appropriate size softener with your water analysis.


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## cgarai (May 12, 2012)

Bob999 said:


> 1. To adjust hardness you must blend raw water and softened water to achieve the desired hardness. Adjusting salt dose is not a reliable way to control hardness--if you adjust the salt dose down you will get soft water (less than 1 grain/gal) for a while and then when the resin is exhaused the hardness will rise to that of the softened water. But with regard to the requirements in your installation manual note it say soft water MAY be under saturated... Do a search for the Langelier saturation index and do the computations to see what the index would be for your water if softened--you may not have a problem with soft water.


This clarifies some things and muddles others. I could not see how salt dosing would affect final hardness, but I had read that here:
http://www.apswater.com/water_softener_capacity.asp 

As for the Langelier Saturation Index, I did as you suggested, but come to no conclusion. Here is why. 

I used 2 website calculators:
http://www.cleanwaterstore.com/technical/water-treatment-calculations/langlier.html

http://www.lenntech.com/calculators/langelier/index/langelier.htm

and both come up with slightly different numbers. I then put the formula for LSI into a spreadsheet and came up with slightly different numbers again. The formula I used is here:
http://www.corrosion-doctors.org/Cooling-Water-Towers/Index-Langelier.htm

It is possible I used the wrong numbers in the formulas I "guessed" that what the online calculators refer to as Ca2+ is hardness in mg/L. 

One thing I noticed that makes a big difference is the final hardness. My LSI goes very negative with .1gr/gal and very positive with 2 gr/gal. This is evident in the formula as the log of small numbers gets more negative. If water softeners really suck all the hardness out then the water is very corrosive according to the LSI




Bob999 said:


> 2. The service flow of a 1 cubic foot softener is typically described as 9 gallons. A properly sized and regularly regenerated softener won't have channeling problems.


I'll use that figure. I have seen 7 GPM/cuft in one place and another mentioned a non-constant figure varying from 9 gpm/cuft at 1cuft to 6.5 gpm/cuft at 2cuft. 



Bob999 said:


> 3. Softening changes TDS very little-perhaps a very small increase.
> 
> If you provide a complete water analysis and the specific softener you have I can suggest salt efficient settings. If you provide family size, specifics of special fixtures like multihead showers and large tubs or anything else than would increase your overall water usage or typical flow rates I can suggest an appropriate size softener with your water analysis.


You asked for it! 

4 people, 3 full baths. One bath with two shower heads and a large tub. My estimation is that most of the time flow rates will not exceed 10gpm and even if they do I don't mind some hardness leakage.

Our water usage over the last year has been 100gal/day for the whole family (25gal/day/person). That comes directly off the water bill. We currently live in a house that requires no irrigation. This calculation is for a house we are building, which is bigger and may lead to less frugal habits, but I hope not too much!

In short, 10gpm and 40 gal/day/person are the figures I'm using.

Water Analyisis:

Alkalinity 189 mg/L 
pH 8 mg/L 
Hardness 12 Gr/gal (205.2 mg/L) 
Iron 0 mg/L 
TDS 300 mg/L 
Manganese 0.53 mg/L 


Based on all the above I get calculate:

160 gal/day
1920 grains/day

Usage is calculated as 7 days + 1 day reserve.
Usage based capacity in cuft:
.51cuft 15#salt/cuft
.77cuft 6#salt/cuft


SFR based capacity is 1.11 cuft
capacity in grains is 33,333 grains

Basing this on a 32k system, I estimate that at 6#/cuft recharge, I should get 11 days between recharges at 160 gal/day. If we actually maintain our usage at 100 gal/day then it goes up to 18 days. 

Did I come close?

Thanks!!

Chris


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## Bob999 (Mar 4, 2010)

There is an important difference between agressive and corrosive water. The LSI is an index of aggressiveness--specifically the tendency of the water to attract (read dissolve) calcium carbonate that it comes in contact with. This is an important measure for things like water districts that use concrete pipes and swimming pool operaters with concrete or plaster pools. Not so important for fiberglass or vinyl pools or pvc piping systems. Also not so important for good quality stainless steel.

Corrosive, on the other hand, is much more related to acidity. I note you have somewhat alkaline water so corrosion is not really an issue and softening doesn't change pH.

I think it is important to note that the literature you posted a link to conditions the warranty on suitable TDS and pH--but in no way conditions the warranty on hardness or the lack of hardness. However, your pH is right on the edge of breaking the warranty.

On the other hand the discussion on p 15 talks about hardness resulting in build-up of lime scale and "may result in premature failure of the heat exchanger ". I know from personal experience that hardness of 6 or 7 grains will cause significant buildup on heat exchangers in a remotely fired hot water heater.

You may want to seek further opinions but mine is that you would probably be better off using your water--but softened-- than using your water blended with softened water to achieve a hardness of 5-7.

Based on your data and your stated willingness to live with higher leakage on occasion I suggest a 1 cubic foot unit with it programmed for a capacity of 16,000 grains, regenerated with 5 lbs, and 8 days override. But you may find that the manganese causes problems with these settings. If so you will need to increase the salt dose--first try 6lbs to see if it resolves the problem and if not then try 7 lbs.


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## zerious (May 3, 2012)

Bob999 said:


> Salt dose is not linear. To illustrate: 15 lbs/cubic foot yields ~ 30K and 6 lbs/cubic foot yields ~ 20K.
> 
> Salt dose for any given capacity is different for SST-60 as compared to standard resin.


Hi again Bob999,

Sorry to jump back in here. I was hoping you might consider answering a couple more questions and one from my previous post.

I'm getting ready to order a 1.0 cubic foot unit with a Fleck 5600SXT and SST-60 resin with a gravel base in a 9" x 48" tank. I have the space so I'm getting the 18" x 33" brine tank because I think it will be easier to clean being round. 

Should the size of the gravel base be the same for SST-60 as it would be for standard resin? 

I was wondering if you would also use an upper basket? The dealer is willing to have the riser tube cut to accept the upper basket which I think mounts onto the valve's base.

Would you be willing to assist me with the settings once I get the unit and confirm what the BLFC and DLFC are? 

Copied from my previous post :

I could not locate the indicated salt dose for SST-60 at the Purolite site.

So, if I go with the 1 cubic foot unit using the SST-60 what would you personally like to see for a salt (sodium chloride) dose setting? 

How often would this regenerate based on 13,440 grains? 

You stated that "Even with a 1 cubic foot unit and SST-60 resin the indicated salt dose for 13,440 grains is about 3 lbs/cubic foot." 

What salt dose would you recommend if I chose to use potassium chloride instead of sodium chloride?

Have a good day!


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## Bob999 (Mar 4, 2010)

zerious said:


> Should the size of the gravel base be the same for SST-60 as it would be for standard resin?
> 
> I was wondering if you would also use an upper basket? The dealer is willing to have the riser tube cut to accept the upper basket which I think mounts onto the valve's base.
> 
> ...


Gravel base for SST-60 is the same as for standard resin.

All upper baskets I am familiar with fit over the riser tube --the riser tube is the same length as without the upper basket because it terminates in the control valve either way. Use, in my view, is optional.

I have no reason to change my suggestion about salt dose with the 1 cubic foot unit. I recommend you set capacity at 14,000 grains, hardness at 8, and days override at 8. Salt dose with most Fleck valves is set by the number of minutes of brine fill. Knowing that one gallon of water dissolves 3 lbs of salt you know that you want to add 1 gallon of water during brine fill. So you check the BLFC-(typically .25 or .5 gpm) to determine how many minutes of brine fill you need.

If you use potassium chloride you will have to increase the salt dose--various sources recommend up to 30% increase. I don't have enough personal experience to tell you any more. My personal opinion is that given your relatively low hardness--and hence relatively low amount of sodium that will be added by the softener, that you are wasting your money to go with potassium chloride unless someone in the household has a specific health reason.

Post again when you have specific values if you have additional questions. I will be traveling and it may take some time for me to get back to you.


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## zerious (May 3, 2012)

Bob999 said:


> Gravel base for SST-60 is the same as for standard resin.
> 
> All upper baskets I am familiar with fit over the riser tube --the riser tube is the same length as without the upper basket because it terminates in the control valve either way. Use, in my view, is optional.
> 
> ...


Thank you Bob999, enjoy your travels, will post back if and when additional information is needed. I sincerely appreciate your time and the quick responses to answer my questions.

With the settings you suggested, if our capacity remains within the 14,000 grains, approximately how often would you estimate that the unit would need to regenerate if the override was not set?


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## Bob999 (Mar 4, 2010)

Every 7-8 days--because the capacity is the estimated usage for 8 days.


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## cgarai (May 12, 2012)

Hi zerious,

I applogize for jumping in on your conversation. I will paste my questions and Bob's replys on a new thread.
Chris


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## zerious (May 3, 2012)

cgarai said:


> Hi zerious,
> 
> I applogize for jumping in on your conversation. I will paste my questions and Bob's replys on a new thread.
> Chris



No problem cgarai, I'm a newbie also, thought your post was interesting and was glad to see Bob999's replies.

I started with a post for my softener because I will be needing to add an indirect water heater to our boiler because I think the tankless coil may be inefficient because of scale and also because we need more capacity for more hot water. Still trying to decide on which indirect to go with.

Good luck with success in resolving your required hardness issues.


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