Hard water from a well
Hardness is calcium and magnesium dissolved from limestone and other rock. It leaves white scale on fixtures and in water heaters, and makes soap work poorly. There's no health limit, and Penn State Extension says it has no harmful health effects. Under about 7 grains per gallon, it usually won't cause major scale.
If you buy something through our links, we may earn a commission. We'd recommend the same thing either way, and we'll tell you when a free option exists. How we make money
What you need to know about hardness
| The limit | None. Hardness has no EPA health limit or secondary standard. |
|---|---|
| How it's measured | Milligrams per liter (mg/L) as calcium carbonate, or grains per gallon (gpg). 1 grain per gallon is about 17 mg/L. |
| The USGS scale | Soft is 0 to 60 mg/L, moderately hard 61 to 120, hard 121 to 180, and very hard over 180. |
| Is it a health risk? | No. Penn State Extension says calcium and magnesium have no harmful health effects and are nutrients your body needs. |
| Where it comes from | Limestone and other carbonate rock. Hard water is most common in the east-central and western U.S. |
| What removes it | A water softener (ion exchange). Penn State puts the hardware at about $500 to $1,500. |
| Before you buy | A softener adds sodium, uses about 50 gallons of water each time it regenerates, and can make water more corrosive. |
Hard water comes from limestone and other rock
Hardness is mostly calcium and magnesium dissolved in water. Groundwater picks them up as it moves through rock, and the USGS says water in carbonate rock such as limestone is usually hard.
Most wells have it. A national USGS study found about 60% of groundwater samples from drinking-water aquifers were hard or very hard, and about 20% were naturally soft. The USGS says hard water is most common in the east-central and western U.S.
Hard groundwater usually has more total dissolved solids too, since calcium and magnesium make up a large share of them.
Hard water causes scale and soap scum, and won't hurt your health
The EPA has no health limit or secondary standard for hardness. Penn State Extension says calcium and magnesium have no harmful health effects, and both are nutrients people need.
The trouble shows up around the house. Hard water leaves white scale on pots, faucets and fixtures, builds up inside pipes and water heaters, and keeps soap from lathering, so you get scum instead of suds.
Here's the USGS scale, with grains per gallon added:
| USGS rating | mg/L as calcium carbonate | Grains per gallon |
|---|---|---|
| Soft | 0 to 60 | 0 to 3.5 |
| Moderately hard | 61 to 120 | 3.6 to 7.0 |
| Hard | 121 to 180 | 7.1 to 10.5 |
| Very hard | Over 180 | Over 10.5 |
The mg/L ranges are from the USGS. Grains per gallon are converted at about 17.1 mg/L per grain. Penn State says levels under about 7 grains per gallon usually don't cause major scale or soap film.
Test for hardness along with everything else
A lab report gives hardness in mg/L, grains per gallon, or both. Get a full panel before you buy a softener. Penn State notes that a softener doesn't fix the more serious problems a well can have, such as bacteria, nitrate or arsenic.
Some states and counties offer free or low-cost well testing.
A water softener removes hardness
A softener runs water through resin beads coated with sodium. The beads trade sodium for calcium and magnesium. When the beads fill up, the softener flushes them with salt brine and starts over.
Penn State Extension says softening is a matter of personal preference, since hardness is a nuisance with no health risk. A few things to weigh:
- Sodium. A softener adds about 7.5 mg of sodium per quart for each grain per gallon it removes. Penn State calls this the main drawback for people on low-sodium diets. The USGS notes that softeners can use potassium in place of sodium.
- Water use. Each regeneration uses about 50 gallons, which adds load to a septic system.
- Corrosion. Penn State says softened water is usually more corrosive, and softeners remove lead poorly.
- Iron and manganese. Penn State says a softener removes clear, dissolved iron, and the Minnesota Department of Health found softeners can lower manganese.
| Option | What it does | Typical cost | Things to know |
|---|---|---|---|
| Water softener | Removes calcium and magnesium for the whole house | $500 to $1,500 for the hardware (Penn State); about $500 to $2,000 installed (USGS) | Needs salt and occasional upkeep |
Questions people ask about hardness
Is hard water bad for you?
No. Penn State Extension says the calcium and magnesium in hard water have no harmful health effects and are nutrients your body needs.
How many grains per gallon is too hard?
The USGS calls anything over 180 mg/L, about 10.5 grains per gallon, very hard. Penn State says water under about 7 grains per gallon probably won't cause major scale or soap film. Above that, it's up to you.
How much salt does a softener add to my drinking water?
About 7.5 mg of sodium per quart for each grain per gallon removed, according to Penn State. Softening 15 grain-per-gallon water adds about 112 mg of sodium per quart. A softener that uses potassium in place of sodium avoids it, according to the USGS.
Will a softener fix my other water problems?
Probably not. A softener handles hardness and some dissolved iron and manganese. Penn State says it isn't a fix for bacteria, nitrate, arsenic or other health contaminants, so test before you buy.
Where this comes from
- USGS Water Science School, Hardness of Water
- USGS Circular 1360, Water Quality in Principal Aquifers of the United States, 1991 to 2010
- U.S. EPA, Secondary Drinking Water Standards
- Penn State Extension, Water Softening
- Penn State Extension, Tips for Buying Water Treatment Equipment
- Penn State Extension, Lead in Drinking Water
- Minnesota Department of Health, Manganese in Drinking Water