Well water is often harder than mains water because groundwater sits in contact with rock such as limestone and dissolves calcium and magnesium, and nobody treats or tests it for you. Connecticut’s Department of Public Health recommends testing a private well every year for basic indicators, hardness included; Vermont’s health department recommends a hardness test at least every five years. Test for iron and manganese at the same time, because they change how you size and set a softener.
On this page
This guide covers why wells run hard, what to test and how often, how to read the results, and how well water changes the softener sums.
Why well water is often hard
The USGS describes hardness as the dissolved calcium and magnesium that water picks up as it moves through soil and rock. Groundwater can spend years in an aquifer, and in limestone, chalk or dolomite that’s a long time to dissolve minerals. Two wells a mile apart can differ a lot if they draw from different rock layers or depths.
Utilities manage hardness for their customers; the USGS notes they generally try to keep water out of the very hard range. A private well gets no such treatment, so its water reaches your taps exactly as the aquifer delivers it.
How often to test a private well
| Source | Hardness | Also in the routine test |
|---|---|---|
| Connecticut Dept. of Public Health | Every year, as one of the “basic indicators” | Coliform bacteria, nitrate, nitrite, sodium, chloride, iron, manganese, turbidity, pH, sulfate, colour, odour |
| Vermont Dept. of Health | At least every five years, as part of an inorganic chemical test | Other inorganic chemicals in the same kit |
Connecticut also advises testing after repairs to the well, pump or pipes, and if the wellhead floods. Whatever your state’s schedule, test hardness before you buy treatment equipment: Penn State Extension notes that testing is what confirms whether hardness is there and at what level, and puts a lab hardness test at about $20.
What to test along with hardness
- Iron and manganese. They stain fixtures and foul softener resin. Manuals such as Pentair’s add 5 gpg to the hardness setting for every 1 ppm of iron.
- pH. Very soft or acidic well water can be corrosive; very hard water is less so.
- Sodium and chloride. Useful before you add a salt-based softener, which adds sodium. Vermont also warns that softener wastewater can raise sodium in nearby wells, so discharge it downhill and well away from the wellhead.
- Bacteria and nitrate. Not related to hardness, but part of any routine well check and the reason a lab test is better than strips alone.
For a quick home reading between lab tests, strips and drop kits work on well water too; our guide on how to test water hardness compares them.
Reading your result
Connecticut’s well testing guide uses the same bands as the USGS: soft up to 60 mg/L, moderately hard 61 to 120, hard 121 to 180 and very hard above that. Labs may report in mg/L, ppm or gpg; divide mg/L by 17.118 for gpg. The full chart is on our water hardness scale page, and the converter handles other units.
If the lab reports only calcium and magnesium, add them as 2.497 × calcium + 4.118 × magnesium to get total hardness as calcium carbonate. That step is explained in our guide to reading a water quality report.
Softening well water: the sums change
Iron counts against a softener’s capacity, so size it on “compensated hardness”: hardness plus 5 gpg for each ppm of iron.
Family of four, 18 gpg plus 2 ppm iron. Compensated hardness is 18 + 2 × 5 = 28 gpg. At 80 gallons per person a day that’s 4 × 80 × 28 = 8,960 grains a day, or 62,720 a week. That calls for a 64,000-grain unit at full salt, or an 80,000-grain unit to run at a medium setting. Without the iron, on 18 gpg alone, the same family would need 48,000 grains at full salt or 64,000 at medium. The sizing guide and calculator take an iron figure directly.
Check the softener’s iron limit in its manual; Pentair’s says iron reduction generally works below 3 ppm and may need special programming and a brine additive. Above that, a dedicated iron filter ahead of the softener is the usual answer. Morton suggests a softener salt with resin cleaner when raw water has more than 2 ppm of iron.
Wells and water heaters
Hard well water scales heaters like any hard water, but some warranties treat well water separately. Noritz’s tankless warranty, for example, excludes damage from “untreated or poorly treated well water” as well as from hardness above 12 gpg. Read the warranty before relying on an untreated well supply; our page on tankless heaters and hard water covers the details.
Frequently asked questions
Is well water always hard?
No. It depends on the rock the aquifer runs through. Wells in granite or sandstone can be soft, while wells in limestone are often very hard. Only a test tells you.
How often should I test my well for hardness?
Connecticut’s health department recommends yearly testing of basic indicators, hardness included; Vermont’s recommends hardness at least every five years. Test again after well work or flooding.
Does a water softener work on well water?
Yes, but size it on compensated hardness if there’s iron, and check the iron limit. High iron or manganese may need separate treatment first.
Can hardness in a well change over time?
It can shift with drought, heavy pumping or work on the well. Regular testing catches changes before they affect your softener setting.
Sources
- Connecticut Department of Public Health: Private well testing
- Vermont Department of Health: Hardness in drinking water
- Penn State Extension: Water tests for households
- USGS FAQ: Water hardness in the United States
- Pentair: Whole house softener owner’s manual (PDF)
- Noritz: Limited warranty, tankless (PDF)
