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

[cgarai]

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

[F6Hawk]

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

[cgarai]

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

[Gary Slusser]

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.

[FleckLander]

"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.

[Gary Slusser]

"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)

That postfill should be PRErefill.

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.

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.

[cgarai]

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

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.

[cgarai]

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

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.

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.

[F6Hawk]

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.

[Gary Slusser]

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.

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.

[cgarai]

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

Oops. Only what is taken from the salt tank needs to be replaced.

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.

On the drawings in the Service Manual (http://www.pentairwatertreatment.com...ow%2042132.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.

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.

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.

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.

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.

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.

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

[F6Hawk]

... it appears to me that flow in and out of the Salt tank is controlled by the BLFC.
Correct; Brine Line Flow Control. Gary mistakenly said DLFC, or Drain Line Flow Control, but I am pretty sure he meant BLFC.

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.

No, the salt is set by your BLFC and the time you set for brine fill. As I mentioned above, setting 24 mins for brine fill @ 0.125 will give you 3 gallons of water in the brine tank, or 9 lbs of dissolved salt after a few hours. This brine sits there, just waiting for the next regen cycle. When the brine/slow rinse cycle starts sucking the water out of the brine tank, it does so until the low water shutoff closes (when all the brine is sucked into the resin tank). The slow rinse continues to happen until the 60 minutes is up (I have heard that it takes about 10-15 minutes to intake all the brine, on average). Salt dosage is NOT set by Brine/Slow rinse at all. It is set by how much water was in the brine tank when the cycle began.

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.

[Gary Slusser]

Oops. Only what is taken from the salt tank needs to be replaced.

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.

On the drawings in the Service Manual (http://www.pentairwatertreatment.com...ow%2042132.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 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..

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.

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.

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.

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

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.

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.

[F6Hawk]

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

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.

[cgarai]

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.