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Old 05-03-2012, 08:00 AM   #1
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Properly Sizing a Water Softener


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 :

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


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.

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.


I would appreciate any insight on choosing the correct size unit and any suggestions on other sites to post this question.

Thank you, Fritz

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Old 05-03-2012, 10:23 AM   #2
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Properly Sizing a Water Softener


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

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Old 05-03-2012, 10:45 AM   #3
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Properly Sizing a Water Softener


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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Old 05-03-2012, 11:44 AM   #4
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Properly Sizing a Water Softener


Quote:
Originally Posted by zerious View Post

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.
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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Old 05-03-2012, 11:52 AM   #5
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Properly Sizing a Water Softener


This is the calculations from the site. For a approximate 7 day recharge you can use a 24000 grain unit.
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Old 05-03-2012, 12:08 PM   #6
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Originally Posted by a7ecorsair View Post
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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Old 05-03-2012, 01:04 PM   #7
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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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Old 05-03-2012, 01:51 PM   #8
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Properly Sizing a Water Softener


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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Old 05-03-2012, 01:55 PM   #9
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Properly Sizing a Water Softener


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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Old 05-03-2012, 02:06 PM   #10
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Originally Posted by zerious View Post
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.
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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Old 05-03-2012, 02:09 PM   #11
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Quote:
Originally Posted by a7ecorsair View Post
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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Old 05-03-2012, 02:20 PM   #12
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Properly Sizing a Water Softener


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...ck+6700XTR.htm

Fleck makes good valves and any one of the valves you are looking at should provide good service.
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Old 05-03-2012, 02:49 PM   #13
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Quote:
Originally Posted by Bob999 View Post
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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Old 05-03-2012, 03:07 PM   #14
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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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Old 05-03-2012, 03:18 PM   #15
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Quote:
Originally Posted by Bob999 View Post
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...ck+6700XTR.htm

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