Water Softeners for Well Water: What They Handle, and How to Size One

How hard is your water?

Hardness is calcium and magnesium. It is reported in grains per gallon (gpg) or in mg/L as calcium carbonate: 1 gpg equals 17.1 mg/L¹. It is not a health issue: Health Canada sets no guideline for hardness¹, and Penn State notes calcium and magnesium are essential nutrients².

Hardness classes · USGS

Class	Hardness
Soft	0–3.5 gpg0–60 mg/L
Moderately hard	3.5–7 gpg60–120 mg/L
Hard	7–11 gpg120–180 mg/L
Very hard	over 11 gpg180 mg/L

The USGS classes are 0–60, 61–120, 121–180 and over 180 mg/L³. The Minnesota Department of Health says a softener might be needed above 7 gpg120 mg/L⁴. Health Canada adds that above 200 mg/L, water is considered poor, and above 500 mg/L, unacceptable for many household uses¹.

Can a softener take your iron?

On a well, this is the first question, not the hardness. Penn State recommends a softener only when the water’s pH is above 6.7, hardness is between 3 and 20 gpg, and dissolved iron is under 5 ppm5 mg/L. Red-water (oxidized) iron fouls the resin². The Minnesota Department of Health adds that some softeners are rated up to 10 mg/L, but 2 to 5 mg/L is the more common limit⁵.

Our take: treat a softener’s iron rating as a ceiling, not a target. Under about 3 ppm3 mg/L of clear-water iron, a softener with a published iron limit is a reasonable one-tank answer. From 3 to 5 mg/L, it can work, with extra cleaning. Above 5, or with red water, put an iron filter in front.

How to size it

Penn State’s method²:

1. Grains used per day = people × gallons per person per day × hardness in gpg.
2. Days between regenerations = the softener’s rated capacity ÷ grains used per day.

Penn State uses 75 gallons per person per day: 4 people × 75 gallons × 10 gpg = 3,000 grains a day, so a 20,000-grain softener regenerates about every 6 to 7 days². Water use varies by home; the USGS estimates 80 to 100 gallons per person per day for indoor use⁶.

If you treat iron with the softener, makers ask you to add to the hardness setting: Whirlpool and Rheem both say add 5 for each ppm of clear-water iron^7,8.

Two settings matter as much as size. Set the softener to your real hardness: set too high, it costs more and wastes water⁴. And choose demand-initiated regeneration, which regenerates by water use rather than on a timer; timer models regenerate whether the resin needs it or not².

Softeners with published iron limits

Salt softener, sold in Canada and the US

Whirlpool WHES40 40,000-Grain Softener

NSF/ANSI 44

Clear-water iron

up to 10 ppm (maker)

Hardness

up to 125 gpg

Rated flow

7.6 gpm

Capacity

40,000 grains at 15.5 lb salt

Efficiency

5,090 grains per lb salt at the lowest setting

Regeneration

demand-initiated

Strengths

• Sold at Canadian Tire as well as in the US
• NSF/ANSI 44 listed for hardness and efficiency
• Extra backwash option for clear-water iron

Drawbacks

• 7.6 gpm is low for a home with several bathrooms
• No red-water, bacterial iron or sediment removal; not certified for iron
• The 5-year warranty needs the maker's cleaner every 4 months

Good fit: a small to mid-size home with hard well water and clear-water iron under about 5 ppm.
Skip it if: you need more than about 8 gpm, or your iron is red-water or bacterial.

Salt softener, US only

Rheem Preferred Plus RHS42

NSF/ANSI 44

Clear-water iron

up to 11 ppm (maker)

Hardness

up to 140 gpg

Rated flow

9.9 gpm

Capacity

42,400 grains at 16.3 lb salt

Efficiency

5,010 grains per lb salt at the lowest setting

Extras

built-in sediment screen, blending valve

Strengths

• Highest rated flow of the softeners here
• NSF/ANSI 44 listed for hardness and efficiency
• Blending valve to adjust the output hardness

Drawbacks

• Sold only at The Home Depot in the US
• No red-water or bacterial iron removal; not certified for iron
• The 5-year warranty needs the maker's cleaner every 4 months

Good fit: a US home on a well that needs close to 10 gpm, with clear-water iron under about 5 ppm.
Skip it if: you live in Canada, or your iron is red-water or bacterial.

Iron filter + softener, sold as a pair

SpringWell WSSS1 / WSSS4 Combo

No NSF/ANSI listing found

Iron (filter)

up to 7 ppm

Manganese (filter)

up to 1 ppm

Hydrogen sulfide

up to 8 ppm

Softener

32,000 or 48,000 grains

Softener flow

11 or 13 gpm

pH

6.5–10

Strengths

• The iron filter sits ahead of the softener and protects the resin
• Iron, manganese, sulfur smell and hardness in one order

Drawbacks

• Three tanks, two drains and power
• No NSF listing found
• Salt to refill

Good fit: hard well water with iron or a sulfur smell above what a softener should take alone.
Skip it if: your iron is above 7 ppm, your well has bacteria, or your pH is under 6.5.

SpringWell also sells the softener alone (SS series, 32,000 to 80,000 grains, up to 20 gpm), but it publishes no iron limit for it, so on a well with iron we would only use it behind an iron filter.

Salt, sodium and potassium

• Salt efficiency. NSF/ANSI 44’s efficiency rating means at least 3,350 grains removed per pound of salt and no more than 5 gallons of water per 1,000 grains⁹. Both softeners above beat it at their lowest salt setting.
• Sodium added. About 7.9 mg/L of sodium per gpg removed, from Health Canada’s figures¹; Penn State gives 7.5 mg per quart². Health Canada says children under 8 generally should not drink water softened with sodium and advises keeping the kitchen tap unsoftened¹.
• Potassium chloride avoids the sodium. GE, a softener maker, recommends setting the hardness 20% higher with it¹⁰. Health Canada advises people with kidney problems to avoid drinking potassium-softened water¹¹.

The septic question

Each regeneration sends about 50 gallons of water to the drain², and sources disagree on what that does to a septic system. Virginia’s health department, citing industry-funded research that found no harm, accepts up to 60 gallons per regeneration and 180 gallons per week without design changes¹². Santa Cruz County, California, says discharge to a septic system is highly discouraged and that many septic tank makers prohibit it¹³. An efficient, demand-initiated softener set to your real hardness keeps the volume down. Check your local rules before you connect it.

Salt-free conditioners on a well

Nebraska Extension calls them descaling devices, not softeners, because they do not remove the hardness from the water¹⁴. A University of Waterloo thesis that tested one technology found treated water formed only somewhat less scale than untreated water¹⁵. If you want soft water on a well, a salt (or potassium) softener is the tool.