That's a lot of iron. I'm sure some more experienced folks will chime in, but you'll have to give more info about your water usage. How many people in the house? Any unusual (soft) water use (like a big aquarium, horse, etc)? What's the water point of entry pipe size? How many bathrooms? Hot tub or jacuzzi?

3 people, 5 loads of laundry per week dishwasher every other day. no horses, no jacuzzi, no aquarium, outside spigots are bypassed. I want to say we have a 1 inch pipe. whatever is standard.

OK. I'm a novice at this, and I welcome the opinion of the more experienced and professionals on this forum, but I will take a stab at it.

For that much iron, if you are not wanting to use a dedicated iron filter, there are many softener design "tweaks" that will help. Things I've learned:

Use a sediment prefilter on the main water line.

Use fine mesh resin instead of standard. Or Purolite SST60. These are more iron tolerant.

Possibly use a KDF MediaGuard insert into the resin tanks. These help to reduce iron, but will not take care of all that iron. The KDF-85 is the higher capacity version for well water.

Use twin tanks for more frequent regenerations without the efficiency loss you would get with a single tank regenerating so frequently. This is because with a single tank you have to factor in a reserve day because the softener will not regenerate exactly when its rated capacity runs out, it will wait until midnight or 2am (whatever it's set for) to regenerate. So you need the extra day of reserve for that in case you use up your capacity earlier than calculated. No such problem with twin tanks. Whenever the capacity runs out, the second tank is put in service while regenerating the first. Additionally, regenerating more frequently will decrease iron fouling of the resin.

Let's consider your hardness. 9 grains per gallon. Adjust this to 33 gpg because of your iron (9+ 12x2). Your manganese doesn't contribute much. At an estimated 75 gallons per day water use per person, that's 150 gallons per day. Calculate that out (150*33) and you need around 5000 grains of capacity per day. Figure regenerations every 4 days to reduce iron fouling the resin, so you need 20000 grains of capacity per tank. Now you probably want to use more salt per regeneration than typical because of the iron. Without the added iron, you could consider a high efficiency salt dose of 6 lbs per cubic foot of resin, but with that much iron you probably want to use more. This is where some pros might be able to help. But let's figure 6lbs so that my post is not completely useless :)

6 lbs of salt per cubic foot will get you 20K grains of capacity. This would be enough for 4 days and you probably don't want to go below 1 cubic foot of resin anyway, even with the light usage that you list. This is the number of cubic feet of resin you would need based on capacity, but not based on SFR. You need to try to estimate your maximum water use in a given instant. If 2 people are showering per day, a load of dishes is running, the washer is running, and the third person flushes a toilet that could be around 12 gallons per minute. This is an estimation of your Service Flow Rate. You will need to try to estimate this as best as you can. Problem is, 1 cubic foot of resin is rated for a max SFR of only 5gpm with a Fleck 9000 series valve. You could go with this if you think your SFR is not greater than that. Or you could oversize it a bit (in regards to capacity) to 1.5 cubic feet and get a bit more SFR of 7.5gpm. But you would still regenerate every 4 days because of the iron. With this you would be using 9 lbs of salt every 4 days, or about 70 lbs per month ... nearly two bags.

So, with those considerations in mind, if you want a good softener only system, and also considering your water hardness, iron, and usage, here's what I would look at in the "DIY" arena. You could buy this and have a local plumber install it:

Fleck 9100SXT valve 3/4"
Twin resin tanks with 1.5 cubic feet of SST60 resin each
2 x KDF-85 MediaGuard inserts in each of the above tanks

A softener like the above from a reputable online dealer would be a bit over $1100.

Again, I'm an amateur who learned all this stuff to try to configure his own system, but I'm sure a few pros and more experienced folks will chime in ...

It would be asking a very lot for any softener to treat 12 ppm of iron reliable and for the long term.

KDF is a wonderful media and in the right application makes a lot o sense. KDF is a lot heavier than resin and requires a higher gpm backwash than resin and that might be a problem on a well and KDF inserts will require maintenance sooner or later.

I favor the right tool for the job. I'd recommend a competent iron filter followed up by a softener. That could be as little as two tanks, the same as a twin resin tank softener.

First of all, I would avoid the KDF suggestion. This may be acceptable on mild applications but not for challenging waters. At only four pounds of media, there would be no problem with backwashing but replacement of media will be needed and soon. It is quite difficult to change this media out. Drops in pressure will happen. Better left out of the equation.

Factoring iron that high I would multiply by four or even five. That would bring the TCH to close to 60. At those numbers a 1.5 x2 twin would work, but I might go with a 2.0 or 2.5 cuft beds. This iron will be a problem if not addressed correctly. I can imagine that plumbi gfixtures are already stained....right?

Greensand filters are being phased out by nearly all water treatment professionals. Aeration and other oxidation systems will cause precipitation in the plumbing and may cause a clogging of the line. Being that your pH is low a single tank timer Calcite filter to help raise pH and filter iron before the softener.

Your iron is very challenging and must be approached right or you will have wasted your efforts and cash.

Andy Christensen, CWS

Sorry, my calculations were off because I calculated for just 2 people rather than 3. So you would have to add 50% anyway for the third person. This suggests a minimum 1.5 cubic foot softener (per tank).

Your iron is just too high for you to use your softener for iron removal effectively. 10 ppm is the max, the ragged edge of what specialized softening resin can reasonably handle. Even then, softening resin is just not suitable for long-term iron removal, particularly at high iron levels such as yours I would use Pyrolox or some such filter for iron removal, followed by a softener for hardness removal. That will be the most reliable and easy for the average homeowner to operate.

No Mediaguard inserts. Period. Trying to make one piece of equipment do the job of two, where different media require different flow rates for regeneration, is just asking for trouble. Not to mention the maintenance nightmare when the Mediaguard needs to be replaced. Don't do it.

What you want is not compatible with reality. However, if you insist on using your softener for iron removal, purchase the cheapest possible softener, use lots of "iron-out" with every bag of salt, pray, and be prepared to replace your softening resin (or your whole softening unit if it is a box-store variety) every 2 - 5 years, depending upon how meticulous you are about your chemicals.