Well Water Softener: Do You Need One, and What Size

Test the hardness first

Hard water is high in dissolved calcium and magnesium. Signs are white scale on pots and fixtures, spots on glasses, and soap that will not lather. Source: Hardness of Water.

A lab report gives hardness in grains per gallon (gpg) or in mg/L. One grain per gallon is about 17 mg/L. Penn State Extension says many softener sellers offer a free hardness test, but an independent lab test is not expensive and protects you from being oversold. Source: Water Softening.

Ask the lab for iron, manganese and pH with the hardness. NC DHHS says to know hardness, pH, iron and turbidity before you install any treatment. Source: NC DHHS. Our list of certified labs by state shows where to send it.

Hardness scale: when water counts as hard

Source: Penn State Extension, Table 1. The USGS uses close cutoffs: 0 to 60 mg/L soft, 61 to 120 moderately hard, 121 to 180 hard, and more than 180 very hard. Penn State says levels below 7.0 gpg will probably not cause major scaling and soap film.

What a softener does, and what it does not

A softener is an ion exchange unit. Water passes through resin beads that hold sodium. The resin trades the sodium for calcium and magnesium. When the resin is full, the softener regenerates: it flushes the resin with salt brine and sends the hardness down the drain. Source: Penn State Extension.

• Removes: calcium and magnesium, and some dissolved iron and manganese.
• Does not remove: bacteria, nitrate, arsenic or sulfur smell. Penn State says softeners will not necessarily remove the more serious drinking water problems.

For those problems, see the well water filter guide, which matches each lab result to a filter type.

Iron and a softener: filter the iron first

A softener can take out a little dissolved iron. The Minnesota Department of Health says 2 to 5 mg/L is a common limit, even though some makers claim more. Source: Iron in Well Water.

Iron that has met air or chlorine turns to rust particles. Penn State Extension says that oxidized iron clogs the resin, so filter it out before the softener. If your report shows iron above the softener limit, put an iron filter ahead of it.

How to size a well water softener

Size it in grains. Penn State Extension gives this example: a house of 4 people uses about 75 gallons each a day, and the water tests at 10 grains per gallon.

1. 75 gallons times 4 people is 300 gallons a day.
2. 300 gallons times 10 grains is 3,000 grains a day.
3. A softener that holds 20,000 grains between regenerations runs about 6 to 7 days per cycle.

You may not need to soften all the water. Penn State says showers, sinks and laundry should probably be softened, and toilets, outside spigots and basement sinks can be bypassed.

Upkeep, salt and water use

• Salt. Keep the brine tank filled. Penn State says the exchange adds 7.5 mg of sodium per quart for each grain per gallon removed.
• Timed or demand control. A timed model regenerates on a schedule and wastes more water and salt. A demand model regenerates after a set number of gallons.
• Septic systems. Penn State estimates about 50 gallons for each regeneration and says to consider the extra load on the drain field.
• Fouled resin. Muddy water, rust and bacteria mats clog the resin. Follow the maker's cleaning instructions.

NC DHHS notes that ion exchange may raise sodium or potassium in the water. After the install, retest the treated water. Source: NC DHHS.

What a well water softener costs

Penn State Extension puts the hardware alone at about $500 to $1,500. The Minnesota Department of Health fact sheet, based on quotes obtained in 2017 and research in 2018, lists $200 to $3,000. Penn State warns against claims that one softener will outlast or out-soften others, because all softeners use the same process. Compare on size, upkeep and cost.

What four states say

• Florida. If a rotten egg smell comes only from water treated by the softener, the Florida Department of Health says the problem is likely sulfur bacteria in the softener. Source: Well Water Facts: Odor and Staining (PDF).
• North Carolina. NC DHHS calls a softener a cation exchange system and lists total hardness, pH, iron and turbidity as levels to know before any install. Source: NC DHHS.
• Michigan. EGLE lists hardness among the standard water quality concerns for private wells. Source: Private Residential Water Well Testing.
• New York. When a water softener is needed to treat hardness, the state health department lists hardness, manganese and iron as the tests to run. Source: Individual Water Supply Wells, Fact Sheet #3.

Not sure the problem is hardness? The treatment picker matches symptoms and results to a treatment, and the treatment map covers every problem.