Need help with potassium solidifying in brine tank (Fleck 7000SXT)

[KineticoUser]

In my home, I have a Fleck 7000SXT water softener that I fill with potassium. I have the valve type (VT) set as difff (downflow fill first, fixed/variable), so the potassium shouldn't be constantly sitting in water. When I discovered the potassium was solidifying on the bottom of my brine tank, I purchased and installed a grid plate for my tank (https://www.amazon.com/dp/B01NARYE4L). Now I find I have to break up the potassium in the grid plate legs before every regeneration in order to get soft water. Do you have any suggestions that wouldn't require this maintenance every cycle? Other than this issue, I love my 7000SXT.

 

[KineticoUser]

What's reducing the water flow through the potassium, is the grid plate legs fill with potassium crystals the size of sand. I have to scoop it out and replace it with large crystals for the water to flow properly. Does anyone know of a way to prevent the buildup of potassium sand in these legs?

 

[Sponsor]

 

[RetiredInGueydan]

The brine should flow downward through the grid and not the legs.

 

[KineticoUser]

That may be true, but if I don't break up the crystals in the legs and on the bottom of the grid, my water doesn't test soft.

 

[RetiredInGueydan]

Do you visibly see water above the grid during brine fill, if so the legs being plugged with salt is irrelevant? You may need to increase the saturation time to allow the solidified salt to fully dissolve.

 

[KineticoUser]

Water does rise above the grid, and SV is set at 120 minutes, per Pentair tech support. I don't understand the reason the water isn't softened if i don't break the potassium up before the regeneration process, but it is softened if I do break it up.

 

[Reach4]

Does some potassium salt remain above the water once the fill occurs?

I was trying to look at the service manual P/N 42775 programming for dFFF Down Flow Fill First, and I did not see a setting for soaking time. Is there a different service manual that covers dFFF programming?


SV gets reference a Software Version elsewhere.

 

[KineticoUser]

Brine Fill (BF) & Service (SV) are listed in item #13 in the master programming mode. Service is the soaking time. I keep some potassium above the water during the soak (SV). I'm aware there are 2 SV settings in the manual, with the second being the Software Version. Here are all my settings:

Fleck 7000SXT settings

DF Display Format GAL Gallons

VT Valve Type dfff Download Fill First. Fixed/Variable

CT Control Type Fd Meter Delayed

C Unit Capacity 20 (X1000) Unit Capacity (grains)

H Hardness 24 Grains of Hardness

RS Reserve Selection rc 75 Gallons

DO Day Override 14 Day Override Setting

RT Regen Time 12:00AM Time of Regeneration

BF Brine Fill 14

SV Service 120

B1 Backwash 8

BD Brine Draw 60

B2 Backwash 3

RR Rapid Rinse 3

UD SYNC

CD Current Day

FM Flow Meter Size t1.2

 

[Bannerman]

While you have programmed the unit to regenerate when 20K grains capacity has been depleted, you have not stated the resin's total softening capacity (ie:32,000, 48,000, 64,000 grains) . If unsure, state the total quantity of resin (ie: 1.0, 1.5, 2.0 cu/ft). If still unsure, state the dimensions of the resin tank (ie: 9X48, 10X54, 12X52). Once we know the quantity of resin, we will likely then be able to offer some further programming recommendations.

Potassium chloride as a regenerant, is far less efficient compared to using sodium chloride, so to compensate, the hardness setting will typically need to be increased 20-25% above the compensated hardness amount.

Since you programmed hardness as 24 grains per gallon, how was that determined?
Is your water source municipal or a private well? If private well, indicate if your most recent lab test indicates if iron and/or manganese is present, and the quantity of each.

You indicate the Reserve Capacity setting is currently programmed at "75 gallons". Is this the actual average quantity of soft water your family consumes in 1-day, or otherwise, how was the 75 gallons reserve determined?

Do you have any suggestions that wouldn't require this maintenance every cycle?

Potassium chloride is significantly more temperature sensitive than sodium chloride. To reduce the effect of varying temperature causing some potassium to re-crystalize in between regeneration cycles, the BFF setting will typically be utilized since the temperature of the Brine will not change significantly from the time the water enters the brine tank, to when the Brine is drawn into the resin tank. If the location of your brine tank is within a fairly stable temperature controlled area, such as a home's basement, suggest resetting the Brine Fill to occur at the end of each regeneration cycle, which will also permit the elimination of the 120-minute delay setting.

I assume this is will be effective in reducing/eliminating your re-crystallation issue. An alternative remedy will be to switch over to using sodium chloride (salt) for the regenerant.

 

[RetiredInGueydan]

The KCL isn't exposed to water for a long enough period time to provide a saturated brine. The brine fill needs to occur at the end of the cycle and not the beginning. A complete system reprogramming needs to be completed to achieve this process.

 

[Reach4]

KCl needs the brine fill shortly below the brine draw, because its solubility changes a lot with temperature. And thus it can solidify if it sits for a long time as is none with NaCl.

Maybe upping the sit time from 120 minutes to 180 minutes would be enough to cause improvement.

 

[Bannerman]

In addition to re-crystallation, potassium is also more prone to forming a crust and caking (forming a solid potassium block) when wetted potassium is permitted to dry in between regen cycles.

Since the current brine fill volume is rising above the grid plate, this will cause some of the dry potassium above the grid plate to become wet and partially dissolved, so the lack of liquid remaining in the brine tank between cycles, will allow the partially dissolved potassium to dry and crust/cake. While you mentioned solidified potassium in the platform's legs, there is likely also crusted potassium above the grid which you are probably breaking up before observing what is contained within the legs.

As potassium dissolves more slowly compared to sodium, the usual recommendation will be to allow 15% longer time for potassium to dissolve compared to the 1-hour normally needed to dissolve sodium. Any crystallized/crusted/caked potassium will require even more time to dissolve, but using hot water will hasten the dissolving of hardened potassium.

I anticipate keeping liquid within the brine tank as recommended above, will likely prevent/reduce the amount of re-crystalization, crusting or caking that maybe currently occuring.

In addition to stating the softeners total capacity, also specify the BLFC (brine line flow control) rate, which is the flow rate for water filling the brine tank. The BLFC info is usually stated on a label located close to the brine line connector.

 

[Reach4]

I wonder if filling the grid legs with something other than KCl salt would move the salt above the grid for better contact when the water rises.

I am thinking of something like mortar or hydraulic cement.

 

[KineticoUser]

That's a lot to respond to, but I'll do my best. I have 1.5 cu ft of resin. I used my Hach 5B test kit to determine hardness of the water coming from my well. Here's my latest well water test (as you can see, Iron and Manganese were not detected):

The reserve capacity was determined by Pentair tech support. I use about 45 gallons a day indoors. They also suggested not allowing the potassium to sit in water for the 2 weeks between regenerations. My brine line flow control rate is 0.25 GPM. I have no problem increasing my SV to 180 minuites.

 

[KineticoUser]

Would pea gravel work in the legs, or will that just lead to the potassium sand solidifying around the pea gravel?

 

[RetiredInGueydan]

KCl needs the brine fill shortly below the brine draw, because its solubility changes a lot with temperature. And thus it can solidify if it sits for a long time as is none with NaCl.

Maybe upping the sit time from 120 minutes to 180 minutes would be enough to cause improvement.

By adding a grid to the brine tank which was set up to function without one, this effectively reduced the water depth by at least 4 inches. That is 4 inches less of KCL that is available for saturation, so the air check needs to be raised 4 inches or an end of cycle brine fill programmed. Adding pea gravel to the legs will provide no improvement and further reduce the amount of KCL available for saturation.

 

[Reach4]

Would pea gravel work in the legs, or will that just lead to the potassium sand solidifying around the pea gravel?

Gravel would consume around 60% of the space.

If potassium salt solidified around the gravel, that would approach the same effect of having mortar filling the space.

Since breaking up the salt impacted in the legs increases the brine concentration, and thus improves softening, that shows that the brine is not getting saturated during the 120 minutes otherwise. Seems to me that would say that 120 minutes is not enough.

Another thought.... while saturated brine will have a higher specific gravity, and therefore sink, the brine above the grid will sink, and water will slowly rise to meet the salt. But the grid will slow the diffusion. So the time to saturate the water below the grid will take longer than if there were no grid.

Shortening the legs on the grid, so that the grid is barely out of the liquid between regens, could minimize the effect.

 

[KineticoUser]

Water rises 4" above the grid during brine fill. Prior to installing the grid, the bottom of the brine tank was one solid mess... probably 8" of solid potassium. Now it is easier to break up whatever solidifies. Should I increase my brine fill time, so the level rises higher? I could increase my brine fill to 21 minutes to raise the level by 50% Soaking the potassium 180 minutes rather than 120 minutes doesn't use more water or electricity, so I might as well do that, but I'm questioning how that might reduce the solidification.

 

[Reach4]

I am just trying to think this through, and I have no applicable experience. You seem to be inclined toward experimenting.

My thought is to try to measure saturation of the liquid below the grid, to see how long it takes for that to become close to saturated. So I am thinking that before you start filling, the resistance is lower. Then as you add water, the resistance would rise initially, and then fall as salt ions diffuse down.

My idea is to put two insulated wires, each poking thru a grid hole, with an uninsulated 1/4 inch to the bottom.

Use an ohmmeter to measure conductance (reciprocal of resistance) which would be roughly proportional to TDS.

How high does the water sit after the brine is sucked out?

Notice that the water sits higher in the brine tube than the level in the bulk of the brine tank. That occurs with sodium salt too. I am wondering if that differential could serve as an indicator of something, but I have not come up with anything.

 

[RetiredInGueydan]

Water rises 4" above the grid during brine fill. Prior to installing the grid, the bottom of the brine tank was one solid mess... probably 8" of solid potassium. Now it is easier to break up whatever solidifies. Should I increase my brine fill time, so the level rises higher? I could increase my brine fill to 21 minutes to raise the level by 50% Soaking the potassium 180 minutes rather than 120 minutes doesn't use more water or electricity, so I might as well do that, but I'm questioning how that might reduce the solidification.

By increasing the brine fill time, you will use more KCL for no added benefit. The air check needs to be raised to compensate for the added grid height.