Sorry about the chart getting all messed up when posted. Apparently the nice spaces I put in get ignored.

size cu ft 6# 10# 15#
9x48 1.0 20k 25k 30k
10x44 1.25 25k 31k 37k
10x54 1.5 30k 37k 45k

If you are sure that the hardness is 17 gpg and you want to assume 1 ppm iron then your math is off.

5040 is your Daily Grains of Capacity needed. 40320 is the Total Grains of Capacity you need for approximately once per week regeneration with a 24 hr reserve calculated in.

You forgot to calculate for reserve... lots of DIYers make that mistake.

You should be shopping for a 2 cu ft softener set at 6 lbs/cu ft of salt (12 lbs total for 2 cu ft) which will give you 3333 grains of hardness removed / lb of salt... pretty efficient. Should regenerate about every 6 or 7 days so set the calendar override for 8 days.

If you go smaller you lose salt efficiency and SFR.

You want to re-plumb the softener so it treats the whole house, not just the hot water.

You can buy a Fleck 5600SXT 2 cu ft softener with Noryl bypass, top basket, and gravel under bed online delivered to your home for about $600

You might consider the same configuration with a Fleck 2510SXT for about $742 or with a Fleck 7000SXT for about $620.

You'll want to start a routine application of Iron Out or a similar product.

Thanks for the quick reply. I knew it was pretty likely that I goofed up something!

My only concern is that the existing softener is puny in comparison. I checked last night and it looks like it is set to consume 10# of salt for each generation. So, when it was working, it must have been regenerating more than once a week? Was that a common thing to do 18 years ago because salt and water were cheap?

(I double checked the numbers from the city. I don't suppose that the water could get any softer on the way to my house?)

It was common to see grossly undersized softeners installed back in the old days and it is STILL way too common to see it now.

Thanks again. So, I see that the 2510SXT can be used on bigger tanks, but I don't necessarily see the difference between the 5600SXT and the 7000SXT. I can get either of these for the same price. Which would be the better choice?

The 5600 series is a tried and true design with decades of reliable service in the field. It is a 3/4" valve and can't be used on larger than 12" tanks. It does not come with a bypass so that is/can be an extra expense depending on the seller

The 2500 series is another tried and true design with decades of reliable service in the field. It does not come with a bypass so that is/can be an extra expense depending on the seller. It is a heavier duty version of the 5600 and can be used on larger than 12" tanks

The 7000 series is a newer design and is a 1"-1.25" valve and comes with it's own unique bypass included in the cost of the valve.

If your plumbing at the softener is 3/4" then flip a coin... if your plumbing is 1" or larger then I'd go with the 7000

With you circumstances I'd choose the 2510SXT with Noryl bypass, top basket, and gravel under bed or the 7000SXT with top basket and gravel under bed depending on the plumbing. JMO...

I ordered the 7000SXT on a 12" x 48" tank (2.0 cu ft) with the top basket and gravel under bed. It should be arriving on Thursday. They really didn't want to sell me the gravel. But, I was insistent. They are sending me "Flint Gravel Underbedding - 0.15 Cubic Feet, 15 pounds", is this the correct amount?

They said they are going to "pre-program" it, but how will I know if they've done that correctly?

Thanks again for all your help!

They should have included the gravel at no charge.

Unfortunately the usual practice for online softener sellers is not to program the softeners they sell for efficiency so you'll have to correct that.

Set the programming...

H (hardness) = 21 (compensated hardness)
C (capacity) = 40k
SF (reserve safety factor) = 20 percent
DO (calendar day override) = 8 days
BF (salt) = 12 lbs (setting is based on BLFC size on the sticker)

To set BF you need to look for a sticker near the brine line connection on the 7000. It will say BLFC xxx gpm or something like that. With that size number you need to calculate gallons of water. One gallon of water = 3 lbs of salt so if the size on the sticker is .125 gpm then you need 32 minutes (4 gallons divided by .125 BLFC size) of BF cycle to get 4 gallons of water into the brine tank to make 12 lbs of salt solution.

Here's a link to the Fleck 7000SXT service manual... http://www.ohiopurewater.com/shop/files/7000SXTServiceManual.pdf

Read the manual. If you are not comfortable diving into the programming... DON'T. Call your seller and have them walk you though the programming but use these numbers REGARDLESS of what they say is correct.

The softener came (in 5 boxes), and I've got it hooked up. Did all the replumbing work so that all the cold water is gonna be soft too.

So, I'm looking to program it, and the BLFC says 0.5 GPM, which would mean only a 8 minute draw. Is that going to be OK?

arrgh, the Brine Draw is set at 60, what I was asking about is the brine fill. But, I guess it doesn't matter, as long as only 4 gallons goes into the brine tank?

Set the BF to 8 (8 x .5 gpm = 4 gallons ( x 3 lbs salt / gallon = 12 lbs salt)

BD (brine draw) and BF (brine fill) are two entirely different cycles... stop thinking!

You should have made the settings I posted and not touched anything else.

H (hardness) = 21 (compensated hardness)
C (capacity) = 40k
SF (reserve safety factor) = 20 percent
DO (calendar day override) = 8 days
BF (brine fill) = 8 (8 x .5gpm BLFC = 4 gallons = 12 lbs)

If you changed anything else set those changes back where they were.

Thanks again. All settings are as shipped. When I ordered the unit over the phone, they asked for the hardness so they could pre-program it. I told them 21, and figured I'd have to reprogram with your numbers. But, they had set the Capacity at 40k, and the reserve at 20%. All I had to do was add the Day Override at 8 and the BF to 8.

Installing it was actually much easier than moving the pipes around. Scooping the resin in to the funnel was fun.

Water is great now. There is a noticeable improvement, probably due to having both hot and cold softened.

The 7000SXT valve looks really nice, is easy to program, and the kids love watching the gallons tick down while the other is in the shower.

The valve says it has the option to program two backwash cycles. Right now, the second one is set to zero (off). Would I see any advantage using the second backwash?

Don't forget... for resin cleaning, once a month use 1/4 cup of Iron Out, Super Iron Out, Rust Pro etc. dissolved into a gallon or two of warm water and pour it into the 4" round tube in the brine tank where the float is and then flush that with a quart of clear water. Then do a manual regeneration

will do the bit with the iron out. thanks!

What about the option for the second backwash cycle, should I enable that, and if so for how long?

You shouldn't need it.