Sodium in softened water

Best for

Anyone deciding whether to drink softened water, especially households where someone watches sodium for blood pressure or heart or kidney reasons.

Wrong fit

If your well water is already high in sodium before softening, test it; the softener adds to whatever is already there.

Tradeoff

Potassium chloride avoids added sodium but costs more and takes more product per regeneration. An unsoftened drinking tap is cheaper but means extra plumbing.

How much sodium a softener adds

A salt softener removes calcium and magnesium by swapping them for sodium. The more hardness it removes, the more sodium ends up in the water.

• Nebraska Extension: about 8 mg/L of sodium for each grain per gallon of hardness removed.
• NDSU Extension: about 8 mg/L (ppm) per grain removed.
• Penn State Extension: 7.5 mg per quart per gpg, which is about 7.9 mg/L.

So use 8 mg/L per gpg as the working figure. The softener does not care whether the hardness was calcium, magnesium or a little dissolved iron; whatever it exchanges is replaced with sodium.

Work out your own number

Sodium added (mg/L) ≈ 8 × hardness removed (gpg)

Then add whatever sodium your well water already had. Many well tests list sodium; if yours does not, ask for it.

EPA’s sodium advisory assumes an adult drinks about 2 liters of tap water a day. Using that, and the Dietary Guidelines limit of less than 2,300 mg of sodium a day that FDA cites:

Coffee, tea and cooking water count too if they come from a softened tap. Water used for showers, laundry and dishes does not add to what you eat.

Putting it in context

FDA says the average American eats about 3,400 mg of sodium a day, well above the 2,300 mg limit. Against that, a glass of softened water is small for most people at moderate hardness. At very high hardness it is not trivial: the table above shows 20 to 30 gpg adding a seventh to a fifth of the daily limit for someone who drinks 2 liters of it.

EPA’s sodium advisory gives two reference points for drinking water:

• 30 to 60 mg/L: a taste-based range. Water in this range is unlikely to taste salty to most people. EPA notes it would supply only 2.5 to 5% of a 2.4 g daily dietary goal at 2 liters a day.
• 20 mg/L: EPA’s guidance level for people restricted to a total sodium intake of 500 mg a day. EPA stresses this figure is for that group and should not be applied to everyone.

The same advisory notes that home water softeners can raise sodium to more than 300 mg/L in drinking water. That happens with very hard water.

Sodium already in your well

EPA’s sodium advisory notes that groundwater typically carries more minerals and salts than surface water, especially where there are sodium mineral deposits or seawater intrusion, and that road deicing salt, water treatment chemicals, water softeners and sewage effluent all add sodium to water. So a well can start out with some sodium before a softener adds any. A lab test that includes sodium gives you the starting point; add the softener’s share from the table above.

People also differ a lot in when they notice it. EPA puts the average taste threshold for sodium in water anywhere from about 30 mg/L to 460 mg/L, depending on the person.

Who should pay attention

• Anyone on a medically restricted sodium diet. The Minnesota Department of Health says such a person should consult their physician before regularly drinking softened water.
• Households with a history of high blood pressure. The Minnesota Department of Health suggests talking to a doctor about drinking softened water.
• Very hard wells. At 25 gpg and above, sodium added is high enough that an unsoftened drinking tap is a sensible default for the whole family.

If you are unsure, ask your doctor and bring your hardness number and the 8 mg/L rule.

Ways to cut the sodium

1. Leave one tap unsoftened. Both the Minnesota Department of Health and NDSU Extension suggest an unsoftened tap for drinking and cooking. The usual approach is to run a separate cold line to the kitchen sink from before the softener. Minnesota also notes that toilets, hose bibs and other cold taps typically do not need softened water, which saves salt as well.

2. Use potassium chloride instead of salt. The Minnesota Department of Health lists this as an option, and most stores that sell softener salt carry it. The tradeoffs:

• It costs more. NDSU Extension’s publication (revised 2022) puts sodium chloride at about $5 to $10 per 40-pound bag and potassium chloride at up to $25.
• It takes more product. WQA says a 13 to 15% higher concentration of potassium chloride is needed to regenerate, and that it forms salt bridges more readily than sodium chloride. Nebraska and NDSU Extension say it binds more strongly to the resin.
• It adds potassium instead. If anyone in the house is on a potassium-restricted diet or medication that affects potassium, ask a doctor first.

3. Set the softener correctly. A softener set to a higher hardness than your water does not add more sodium per gallon, but an inefficient salt setting wastes salt and sends more to your drain and septic system. See water softener settings.

4. Point-of-use treatment. Some households add a drinking-water system at the kitchen sink. If you go this route, check the product’s certified performance data for sodium or total dissolved solids reduction rather than relying on marketing.

5. Do not soften at all. If your hardness is moderate and the sodium question matters more to you than scale, you may not need a softener. See do you need a water softener for well water.

A salt-free conditioner adds no sodium, but it also does not remove hardness and usually needs iron-free water. See salt-free vs salt water softeners.

Outdoors, plants and appliances

NDSU Extension says softened water is not recommended for watering house plants, lawns and gardens because of its sodium content, or for steam irons and evaporative coolers, where distilled or reverse osmosis water is the better choice. WQA’s best-practice booklet recommends bypassing outside sill cocks so softened water is used only inside the home, and the Minnesota Department of Health notes that hose bibs typically do not need softened water. If your outdoor taps are on the softened line, moving them to the unsoftened side saves salt and keeps sodium off the garden.

What softening takes out

Penn State Extension notes the other side of the trade: softening removes calcium and magnesium from the water, so you lose whatever small amount of those minerals your drinking water was contributing to your diet. For most people, food is the main source of both.

Bottom line

Multiply your hardness by 8 to get the sodium a softener adds in mg/L. For most healthy adults at moderate hardness, it is a small fraction of daily intake. For anyone on a sodium-restricted diet, or for very hard wells, keep the drinking tap unsoftened or use potassium chloride, and talk to a doctor. If you need to convert your lab result first, see water hardness levels.