Proper choice of water softener system using resin bed volume and efficient salt


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Old 10-22-13, 10:09 AM
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Proper choice of water softener system using resin bed volume and efficient salt

I have a private well with the following water properties:
26 GPG Hardness
2.5 ppm Iron
0.5 ppm Manganese
This results in a total Hardness of about 40 GPG
4 persons in the household @ 75 g per day per person = 300 gallons per day
300 gpd * 40 gpg = 12000 grains of hardness per day
References I have read show that standard softener resin will regenerate about 17,000 to 18,000 grains per cubic foot of resin at a salt dosage of 4lbs per cubic foot of resin. These references suggest that to get much higher regeneration capacity requires going to more inefficiently higher salt dosages. I would like to keep my salt dosage down to about 4 lb per cf of resin. Therefore:
17000 g per cf / 12000 g per day = about 1.4 days between regeneration per cf of resin.

I plan on purchasing a dual tank softener using the 9100SXT valve. The first question is, How many cubic feet of resin?
With the Iron content I have in my water I assume I should regenerate each resin tank at least once every 4 or 5 days? Therefore I need to avoid oversizing the resin bed, and have calculated that with the salt dosage of 4lbs/cf resin I would want between 1.5 and 2 cubic feet of resin so that I am regenerating each tank every 4 to 6 days. Is my math correct?
Other questions?
1.What dimensions resin tank?
2.Gravel in tank, yes or no?
3.Is it straight forward to set up the salt dosage to get optimum efficiency of salt with the Fleck 9100SXT?
4.I have plumbing from the softener on, The 9100SXT comes in internal and 1 internal, Will the 1 help with lower pressure drop in my system? How can I minimize pressure drop across the softener?
5.I would prefer a large brine tank. Is salt bridging a big problem in brine tanks? How can I avoid problems but still use a large tank? The tank I most commonly see is 18 * 40.
 
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Old 10-22-13, 11:45 AM
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You are asking for headaches by using only 4 lbs salt per CF. The iron alone will require more salt useage. I don't know where you read about only using 4 lbs salt, but real world will require you tom use 8-10 lbs per regen with the amount of iron you have. Even if the iron were removed prior to the softener, using 6-8 lbs per CF is more realistic.
 
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Old 10-22-13, 06:31 PM
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Salt dosage rate efficiency is documented here,

Achieving Brine Efficiency

I just did the math. Are you saying that the Iron hardness equivalents is greater than 5 X normal hardness? I would like to see the reference for that. Salt dosage is only meaningful in the context of resin volume and time between regeneration. If my objective is to reduce time between regeneration then I need to reduce salt dosage. Of course with a very large resin volume and a very large dosage I could extend the regeneration time to very long intervals..... not a good idea if I want to keep the resin from fouling from iron.
 
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Old 10-23-13, 05:57 AM
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You are correct. The longer runs between regens with iron, the more chances of fouling out the resin or the unit not having enough time to rinse all iron. With using only 4 lbs of salt per CF to regen, you get a higher the chance of hardness bleed through not taking into account the iron. You really should not use a softener to remove high iron even though it will work. What you are trying to do is remove the iron and use less salt as possible which does not work. You should set the day override to regen if the the volume of water has not tripped the meter or set the meter lower than needed to cause a regen sooner. With or without iron, you should not be 4 lbs of salt per regen. In my experience, 6 lbs is the min.
 
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Old 11-02-13, 07:08 AM
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Hi biermech, well i finished installing my new softener two nights ago. Just to review,
I have a private well with the following water properties:
26 GPG Hardness
2.5 ppm Iron
0.5 ppm Manganese
This results in a total Hardness of about 40 GPG
4 persons in the household @ 75 g per day per person = 300 gallons per day
300 gpd * 40 gpg = 12000 grains of hardness per day

i installed a dual 12" x 52" tank system with gravel underbed and 2 cf of 10% resin in each tank. system has a Fleck 9100SXT control valve. The software has the cycles in the following order and I set each cycle to the minutes in parenthesis;

back wash (BW 10 min)
brine draw and slow rinse (BD 60 min)
rapid rinse (RR 10 min)
brine fill (BF 8 min)

by setting the brine fill to 8 minutes I am putting 4 gallons of water in the brine tank (0.5 gpm on label, but i measured it to confirm too) 4 gallons @ 3lbs per gallon is about 12 lbs of salt per regeneration. This will not "completely" regenerate 2 cf of resin (64000 grains) but should regen 40,000 grains which is where i set the software capacity (C) setting too. By "short" salting I should get better salt efficiency. NOW the question. I have read that a particularly when short salting it may be a good idea to have a second back wash cycle after rinsing to redistribute the resin bed. The 9100SXT software allows you to choose a different valve type which has 2 backwash cycles but I tried that and it was clear to me that there must some additional change in the hardware that makes it possible to actually implement a different cycle order (perhaps changing out cams?) Does anyone know much about this?
 
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Old 11-02-13, 07:49 AM
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I don't believe you would have to change a cam or anything to get a 2nd backwash. Most program these days allow for a 2nd backwash. The 2nd backwash is to help rid the resin of iron prior to brining. With 6 lbs salt per CF, you are getting 24K so the system should be set for 48k and not 40K. Make sure to use some type of resin cleaner. Without it, iron will build on the resin and foul it prematurely.
 
 

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