Removing iron with a softener, will not result in efficient operation no matter which size softener or salt setting is utilized.
Each 1 ppm iron, will consume the equivalent capacity as removing 85 ppm (5 grains per gallon) actual hardness, so in consideration of 850 ppm actual hardness (=~50 grains per gallon), + 12.5 gpg for iron, results in 62.5 gpg hardness. In addition, because hard, iron laden water will be utilized for regeneration, additional capacity will be depleted during each regeneration cycle, so to compensate, the hardness amount will need to be multiplied by 1.3, thereby arriving at a hardness setting of 81 gpg.
With 2 ppl, estimated to utilize 150 gallons/day X 81 gpg = 12,150 grains per day softening load
A softener equipped with 2ft3 resin (64,000 grains total capacity), for efficiency, will be typically programmed to regenerate when 48,000 grains has been depleted. To regenerate 48K grains will require only 16 lbs salt each cycle. FYI, to regenerate all 64K grains each cycle, would require 40 lbs salt (20 lbs per ft3), which would be highly wasteful and inefficient @ only 1,600 grains per lb.
48,000 gr / 12,150 = 3.77 days - 1 day reserve = an estimated regeneration frequency of 2-3 days
A softener equipped with 2.5ft3 resin (80,000 grains total capacity), will be typically programmed to regenerate when 60K grains has been depleted. To regenerate 60K grains will require only 20 lbs salt each cycle.
60,000 gr / 12,150 = 4.93 days - 1 day reserve = an estimated regeneration frequency of 3-4 days.
In addition to the inefficiency due to the iron, the softener will require frequent and ongoing additional maintenance to clean the resin to reduce the amount of iron fouling.
As softeners utilize a process of ion exchange to remove hardness ions (mainly calcium & magnesium), exchanging them with sodium ions, a softener will not remove the sodium which is already in the well water, but will further increase the amount of sodium in the water supplied to the home's fixtures. As such, a Reverse Osmosis system could be added for supplying sodium free water for drinking & cooking.
Although a dedicated iron reduction system prior to the softener would reduce the softening load, a twin tank softener would permit the full amount of capacity regenerated each cycle, to be fully utilized. A twin tank softener utilizes 2 identical resin tank's, with only one tank providing soft water at one time. Once the programmed capacity in the 1st tank is depleted, the alternate tank will immediately come online to supply soft water. As regeneration will not need to be delayed until a specific time, usually during the night when soft water is usually not needed, then no reserve capacity will be required, and regeneration can occur anytime throughout the day without consideration of fractions of days which may or may not be actually utilized with a single tank softener.
One other method to improve salt efficiency somewhat when hardness is excessive, is to utilize 2 softeners in series, each regenerated with different salt settings.
A lower salt setting will increase salt efficiency, but will result in low water quality due to high hardness leakage through the resin. In addition, because the Capacity setting will be low, regeneration will need to be frequent.
When 2 softeners are utilized, the 1st softener would be larger than the 2nd, and would be programmed with a low salt setting. The 1st softener will remove the bulk of hardness and iron, but the outflow will be of low quality due to the amount of hardness leakage through the resin bed.
The 2nd softener will remove the remaining hardness from the 1st softener, and with a higher salt setting programmed, the qualty improving the quality of soft water supplied to fixtures will be improved. Because the 2nd softener will remove substantially less hardness and iron than the 1st, and because the Capacity and salt setting will be higher, the 2nd softener maybe considerably smaller in resin capacity than the 1st, but will require less frequent regeneration.
