Salt Dosage and Fleck 6700XTR, or any head for that matter

Discussion in 'Water Softener Forum, problems, installation and r' started by cgarai, Jun 28, 2012.

  1. cgarai

    cgarai New Member

    Messages:
    21
    Location:
    Sonoma County
    Hi,

    Trying to figure out the salt dosage settings on this Fleck head though I believe the following would apply to most electronic heads. It is a downflow brining head. Although it has a salt dosage in the menu it is only available for the upflow configuration. I can set the head to be upflow, but the valve body isn't set up for it and I don't know what happens if I set it to upflow. Does it open the valves to do down flow, but provide the other setting features offered in upflow? I haven't tried experimenting yet.

    PLEASE CHECK THE FOLLOWING CALCS TO SEE IF I HAVE THE CONCEPTS. THANKYOU!

    So I assume that I need to control salt dosage based on the following:

    1. Resin Volume
    2. BFLC flow rate
    3 Salt dosage

    From these numbers I can calculate the required brine and rinse time.

    So for my system:

    Resin Vol = 1.5 cuft (Nominal 48K grains capacity)
    BFLC = .125 gpm
    Salt dosage = 6#/cuft

    The other required bit of info is the amount of salt in the brine. Brine Conc = 3#/gal is assumed. I have seen it listed as low as 2.6#/gal

    The calcs run like this (in my head):

    Salt required = Resin Vol * Dosage = 1.5 cuft * 6#/cuft = 9 # of salt

    Brine (gal) = Salt Req / Brine Conc = 9#/(3#/gal) = 3 gal of brine.

    Brine&Rinse time = Brine/BFLC flowrate = 3 gal/(.125gal/min) = 24 min

    Does that seem correct? I can't see another way the amount of salt could be controlled.

    The remaining question is what to enter for system capacity on this Metered valve. The nominal capacity is 48kgr, but that is at a salt dosage of 15#/cuft. My understanding that

    Salt Dosage Capacity
    6#/cuft 20Kgr/cuft
    15#/cuft 32Kgr/cuft

    so my system capacity is

    48Kgr * (20kgr/cuft)/(32kgr/cuft) = 32Kgr.

    My assumption is that 32kgr is the proper number to enter for capacity in the setup for this head.


    My understanding is that for a given head/valve/resin tank combo the brine time is what controls the salt dosage. For a bigger BFLC flow rate, less time is needed, for a larger resin volume more time is needed.

    My other understanding is that the system capacity setting on any head must be set to a compensated level based upon salt dosage. The exception to this would be a head that allows you to set the salt dosage directly. In that case the head does the above math and sets the brine time appropriately.

    The people that sold me my unit are telling me that setting for lower salt dosages is a flawed concept and their setup instructions do not adjust brine time for system capacity. I just can't believe that is true from everything I have read.

    Thanks,

    Chris
  2. F6Hawk

    F6Hawk New Member

    Messages:
    166
    Location:
    Alaska
    For the most part, correct calculations. But there is the theoretical max of a softener (48K in your case) vs. the practical capacity (45K). The normal dosing numbers are:

    1 cu ft 1.5 cu ft
    4# - 16K 24K
    6# 20K 30K
    8# 24K 36K
    10# 27K 40.5K
    15# 30K 45K

    Also, 48 * 20 / 32 = 30K, not 32K
  3. cgarai

    cgarai New Member

    Messages:
    21
    Location:
    Sonoma County
    Thanks F6Hawk for checking my arithmetic! And for the reply. Maybe it is me, but it seems that I haven't been able to find that info in one clear place. Is there a sticky somewhere that explains this? If not, there should be.

    Thanks again,

    Chris
  4. Gary Slusser

    Gary Slusser That's all folks!

    You need to come up with how many gallons between regenerations you need/want. That gives you the length of time (days) between regenerations. And it and a calculation of your peak demand flow rate should have been done before you buy a softener.

    Then you take the K of capacity you need for the regeneration schedule (gallons over how many days) and find the salt efficiency you want and then the lbs of salt (3lbs/gal of refill) is required to make that happen. You would add to that any reserve capacity you need IF your control valve doesn't have variable reserve, which yours does.
  5. FleckLander

    FleckLander New Member

    Messages:
    16
    Location:
    Wisconsin
    "From these numbers I can calculate the required brine and rinse time."

    Just so everyone is on the same page, it's my understanding that the standard softener cycles are backwash, followed by brine draw/slow rinse, followed by rapid rinse, followed by brine fill. (Assuming no double backwash and postfill brine fill)

    The cycle that you want to set to 24 min to get your desired 9 lb total salt dose is the BRINE FILL, not the "brine and rinse time". Your seller is probably taking your referring to "brine and rinse time" as the brine draw/slow rinse cycle which would be more like 60 minutes for a generic setting.
  6. Gary Slusser

    Gary Slusser That's all folks!

    That postfill should be PRErefill.

    Good catch.

    The 60 minutes slow rinse/ brine draw is a default setting from the factory, as all the settings are. Depending what and how much of it is in the water, like iron, I usually shorten that cycle time along with the backwash and final rinse cycles.
  7. cgarai

    cgarai New Member

    Messages:
    21
    Location:
    Sonoma County
    Thanks, I did all that before hand. Now I'm just trying to get the system setup. In my case the SFR set the size of the system quite high compared to my average water use and hardness, which is quite low compared with the nominal 75 g/day/person normally assumed. Thus the time between regens will be at the upper end (20days plus if our water usage doesn't change) of what I have read is acceptable.

    Chris

    Last edited: Jun 29, 2012
  8. cgarai

    cgarai New Member

    Messages:
    21
    Location:
    Sonoma County
    Now that is not my understanding at all. The Brine Fill cycle refills the brine tank. The Brine/Slow Rinse (I was a little sloppy with my terminology before) is where brine is being fed into the resin tank along with water. At least that is what the service manual shows.

    I hadn't really considered the Brine Fill cycle. This will depend on the size of the brine tank and the flow rate into the tank. There is an float type shut off valve, but it probably best to adjust the time so that one isn't relying the float valve.
  9. F6Hawk

    F6Hawk New Member

    Messages:
    166
    Location:
    Alaska
    As you noted above, you need 3 gallons of water to put 9 lbs of salt into solution; the way you get 3 gallons is to divide 3 by your .125 to get 24 minutes of BRINE FILL time. This happens at the end of the regen cycle, leaving water for the next cycle of Brine/slow rinse. The industry standard seems to be 60 minutes on the draw, but you will have sucked out all the brine in about the first 20 minutes or so.
  10. Gary Slusser

    Gary Slusser That's all folks!

    The size of the salt tank has nothing to do with it.

    You can't get brine until the salt is dissolved, and that happens in the brine tank after the brine refill water has been added to the brine tank. The brine refill is added by the minute at your DLFC rating (.125 gpm). And that float, it is not used to stop the brine refill water flow, it is a safety float operated shut off valve to prevent salt brine from overflowing the tank onto the floor if something goes wrong and the brine water rises too high, which can happen fairly frequently.

    Your control valve allows for PRE refill, meaning the refill water is added before a regeneration starts, as the first cycle position, then there is a pause and after that the control valve starts the backwash, slow rinse/BRINE DRAW meaning suck the brine water out of the brine tank into the resin tank. You can't have brine draw without the slow rinse water flowing.

    It takes 2 hours for the brine refill water to totally dissolve all the salt needed for the regeneration salt dose. Post refill is done as the last cycle position of a regeneration.

    BTW, water companies say the average gals/person/day is 60, and its been that way for a very long time but especially since shower heads, dish/clothes washing machines, toilets and sink fixtures have had to meet water conservation mandated maximum gpm etc. ratings. I've used 60 gals since the late 1980s and I have no idea why Fleck still uses 75 unless it's to pad the reserve capacity of the softener for uninformed dealers.

    Lastly... the 60 minutes of slow rinse/brine draw is a factory default setting, and many dealers would rather not be bothered in changing it or informing their customers of why it should be changed, or to what it should be changed to based on their water quality and the size of the softener. The rest of the original programing is factory default also and each control valve manufacturer has their own default settings. Sad to say that most dealers, plumbers etc. do not know what to set them to so they say the settings are just fine.
  11. cgarai

    cgarai New Member

    Messages:
    21
    Location:
    Sonoma County
    Oops. Only what is taken from the salt tank needs to be replaced.


    On the drawings in the Service Manual (http://www.pentairwatertreatment.co...als/6700XTR Service Manual Downflow 42132.pdf) it appears to me that flow in and out of the Salt tank is controlled by the BLFC. My guess is that since brine draw during Brine/Slow Rinse is done with a venturi and Brine Tank Fill is done with line pressure, that the refill rate will be higher than the draw rate. Especially since the draw is flowing heavier brine uphill and the refill is straight water down hill. Irregardless, the Brine Tank Fill time should be set so that the water flowing into the tank doesn't activate the overflow, at least not for too long.


    I can't find any mention in the Service manual for the 6700XTR about PRE refill or fill. Perhaps you could give me a page number.


    60 or 75 GPDP doesn't make much difference to me. For the past year we have averaged 100 GPD for four persons. This system is going in a bigger house, but it is still the same 4 people. I ran sizing calcs the system both at 25 GPDP and 40 GPDP just in case.



    That seems nuts. The salt dosage is set by the Brine/Slow Rinse time, all else being equal. In a small system you might end up with much over 15#/cuft. In a large system less than 15#/cuft, which is OK, but the metered Reserve calcs in the valve will be inaccurate. All of these numbers interact, so it seems to me that the heads should all have a Salt Dosage setting. (The 6700XTR does, but only in Upflow mode.) The only thing the valve would not know at this point is the salt efficiency curve of the resin being used, but even assuming the standard would cause only a small error.

    Thanks,

    Chris
  12. F6Hawk

    F6Hawk New Member

    Messages:
    166
    Location:
    Alaska
    That is the truth as I know it, your Honor!

    BTW, 25 GPPPD is awesome. Since I got my softener, I have tracked usage, and we are about 41 GPPPD for a family of 4, two teens.
    Last edited: Jun 30, 2012
  13. Gary Slusser

    Gary Slusser That's all folks!

    It has to be added before it can be removed so as part of installation of the softener you add the gallons for your salt dose and enough to get them above the air check height of 2.5" minimum. That's for post refill, for pre refill you add the 2.5". Otherwise a post refilled softener will not have any water in the salt tank to regenerate with. Pre will add the salt dose volume at the beginning of the regenration but... slow rinse/brine draw won't be able to suck out but the water above the air check.

    I typed Dlfc but it should have been the Blfc (it matched your Blfc .125 gpm). Your DLFC should be 2.4 gpm.

    Yes the BLFC and line pressure is correct but both go through the BLFC so in and out, both are the same volume of water..

    Then you may need to get the manual or instructions to show you how to get into the 'installer' programming or I am wrong and the XTR timer doesn't have that option. Or a selection you've already made prevents it from being an option. I don't know much about the XTR timer.

    The 75, 60 or whatever gal/person/day is critical to correct programming.

    Nope, the salt dose is set by the volume of water added in the refill cycle position.

    The slow rinse/brine draw cycle sucks out all the water in the salt tank down to the air check in the brine pickup tube (for Fleck and Clack, Autotrol has th eair check up on the control valve).

    Using more than 15lbs per cuft of resin is a waste of salt.

    The only inaccuracy if any is in the programing or a mechanical malfunction which will be caused by a blocked injector. injector throat or screen or a blocked drain line or loose brine line fittings or some internal part in the control valve like worn/damaged seals or piston.

    Many control valves/heads set the salt dose by the number of minutes of brine refill or accept the actual number of lbs and use their computer to convert the lbs into minutes of brine refill flow but there are some that don't and must use a float in the salt tank; like expensive Kinetico softeners and some big box store brands.
  14. F6Hawk

    F6Hawk New Member

    Messages:
    166
    Location:
    Alaska
    Why do you say this? I can see it making a difference on a timer-based system, but on a meter=based one, it regens when the gallons/grains programmed have been used up. Planning on using 75 GPPPD, then only using 40 GPPPD just means you get more days between regens.
  15. cgarai

    cgarai New Member

    Messages:
    21
    Location:
    Sonoma County
    OK, I think I finally understand something that I had a complete misconception on. The Brine Fill cycle places a metered amount of water in the brine tank. The Brine/Slow Rinse cycle sucks all of that water out, now laden with salt.

    Now I'm curious about the instructions from the dealer on my unit. For the Brine Fill stage the recommend the following:

    Step 4 (BF): see the appropriate minutes for your system on the chart below.
    24,000 Grain system = 8 minutes
    32,000 Grain system = 10 minutes
    40,000 Grain system = 11 minutes
    48,000 Grain system = 14 minutes
    64,000 Grain system = 16 minutes
    80,000 Grain system = 18 minutes
    96,000 Grain system = 20 minutes
    110,000 Grain system = 22 minutes

    Two questions about those numbers:
    1. Why isn't the time linear? Should not a 48K system require twice as much salt and there for twice as much time as a 24K?

    2. Calculating the BLFC gpm from the above:
    Assume:
    32K = 1 cuft resin
    15#/cuft dosage
    3#/gal salt in brine

    BLFC (gpm) = 1cuft * 15#/cuft / (3#/gal) / 10min = .5 gpm

    The 6700XTR has the BLFC setting, which is currently set at .125gpm. If I use the above recommendation and the BLFC in the valve matches the setting it comes with, then my salt dosage will be 3.5 #/cuft.

    Sorry to flog this to death, but I like to understand systems and in this case I have found the documentation inadequate.
  16. F6Hawk

    F6Hawk New Member

    Messages:
    166
    Location:
    Alaska
    You got it on the brine fill. The amount of salt used is determined by the amoung of gallons added at the end of the cycle, assuming that 3 lbs/gal of salt will dissolve. Next cycle, ALL of that brine water will be sucked into the resin during the brine/slow rinse cycle.

    As for your other questions, I cannot say why they gave you those numbers if you have a .125 BLFC fitting. Or a .5 BLFC, for that matter. Using the 1.5 cu ft tank, if you have a .125 BLFC, you will fill 1.75 gallons of water or about 5.25 lbs of salt. Using the .5 BFLC, that would be 7 gallons/21 lbs of salt. Neither makes sense to me, unless they programmed the valve differently than mine is. But yes, a 2 cu ft system would require exactly twice the BF time of a 1 cu ft system to have the same ratio of salt/cu ft.

    Unless the 6700 works drastically differently than my 7000SXT, the BLFC determines the amount of brine created. For your system, .125 X 24 = 3 gallons of water, 9 gallons of salt, or 6 #/cu ft.

    Any chance you could post all of the programming instructions that came with your valve?
  17. Gary Slusser

    Gary Slusser That's all folks!

    Because it is the truth but you're right, using 75 gals/person/day and then programming for 40 gals changes the meter setting and you get many more days between regenerations than you should. Which I say is way too long for a residential softener.

    BTW, a timer based valve is set for the number of days between regenerations based on the estimated gals used per day so there is no difference.
  18. Gary Slusser

    Gary Slusser That's all folks!

    There is no metering of the brine reflll, the flow rate gpm is controlled for a set amount of time. It works the same for the DLFC and the other cycle positions of the regeneration; gpm controlled for X minutes and all the cycle positions are adjustable and the dealer is supposed to do the adjusting or tell their customer how and what to set them at. As I said before, most dealers, plumbers, drillers, store clerks etc. don't know what to set them to.

    The default BLFC for a 6700 is .125 gpm. You need to make sure you have a .125 and use whatever gpm BLFC is physically in the valve. The salt dose minutes you were given maybe for a .5 gpm BLFC which is the most common BLFC.

    No it isn't linear and my web site sizing page explains how it actually works. The salt efficiency increases in a larger volume of resin, and it is what it is regardless of why. The max salt dose is 15 lbs/cuft and it gives you 30K of capacity/cuft; that gets you a 2000 grain/lb salt efficiency.
    Last edited: Jul 2, 2012
  19. F6Hawk

    F6Hawk New Member

    Messages:
    166
    Location:
    Alaska
    He's not asking about the linearity of the amount of salt used to regenerate; rather, he is asking why the time to fill is not linear, which it SHOULD be. A 2 cu ft system will require twice as much brine as a 1 cu ft system, assuming the same dosage of salt.
  20. F6Hawk

    F6Hawk New Member

    Messages:
    166
    Location:
    Alaska
    There is a huge difference... using the metered valve, your estimated GPPPD has no effect on the system, other than the aforementioned days between regens.

    In a timed system, your GPPPD actually DEFINES the days you set between regens, and can be terribly inaccurate if you don't properly estimate your usage. For example, if one were to use a 60 GPPPD estimate and program the timer accordingly, but only had a 40 GPPPD's worth of use, then salt will be wasted every regen, making the system very inefficient, particularly at the higher salt concentrations.
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