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Hard Well Water: Signs, Testing and How a Softener Works
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Signs of hard water (Penn State Extension)
- Gray or white deposits when water is heated.
- Scale on pots and fixtures.
- Soap film on skin and detergent curds in the washing machine.
- Scale on water heaters, which can shorten their useful life.
- Calcium and magnesium can plug pipes and make soaps and detergents less effective.
How hard is yours?
| Class | Grains per gallon (gpg) | mg/L (ppm) |
|---|---|---|
| Soft | Less than 1.0 | Less than 17 |
| Slightly hard | 1.0 to 3.5 | 17 to 60 |
| Moderately hard | 3.5 to 7.0 | 60 to 120 |
| Hard | 7.0 to 10.5 | 120 to 180 |
| Very hard | Greater than 10.5 | Greater than 180 |
Source: Penn State Extension, Water Softening. 1 gpg is about 17 mg/L.
Ask the lab for hardness along with iron and pH. See the testing guide. Hardness does not replace the yearly bacteria and nitrate tests.
How a water softener works
Softeners use ion exchange. Water passes through resin that trades its sodium ions for the calcium and magnesium in the water. When the resin is spent, it is backwashed with a salt (brine) solution that carries the hardness minerals away (Penn State Extension).
Trade-offs to know
- Sodium: The exchange adds 7.5 milligrams of sodium per quart for each gpg of hardness removed. This matters for low-sodium diets.
- Water use: Each regeneration uses about 50 gallons of water, which adds load to a septic drainage field.
- Hardware cost: Penn State Extension puts hardware alone at roughly $500 to $1,500, with installation and maintenance on top.
- Timed vs demand models: Timed models regenerate on a schedule and waste more water and salt. Demand-control models regenerate based on water use.
- Iron: Dissolved iron below 5 mg/L can usually be handled when pH is above 6.7 and hardness is 3 to 20 gpg. Oxidized iron clogs the resin, so filter first.
Keeping it working
Keep the brine tank mixed and stored properly. Muddy water can clog the resin. Bacteria and fungi can form mats in the resin, and periodic cleaning with chlorine bleach or disinfecting the water beforehand helps. Check the maker's instructions before adding any chemical, and replace resin that cannot be cleaned (Penn State Extension).
Not sure what's wrong with your water?
Our free checker matches what you see, smell or taste to the likely cause, the test to ask for and the type of treatment that fits.
Open the well water checkerComparing softeners and whole-house systems?
Treatment should match a lab report, not a guess. Once you know what is in your water, a licensed water treatment professional can size a system for it. You can also look at whole-house systems sold online.
How well water systems workSee whole-house system optionsRelated guides
- Water softener cost
- Salt-free vs salt-based softeners
- Whole house softener sizing
- Water softener installation
Common questions
What is hard water?
Water with a lot of dissolved calcium and magnesium. Penn State Extension grades it as soft below 1.0 grains per gallon (gpg), slightly hard at 1.0 to 3.5, moderately hard at 3.5 to 7.0, hard at 7.0 to 10.5 and very hard above 10.5.
How do I convert grains per gallon to mg/L?
Penn State Extension says 1 gpg is approximately 17 mg/L (ppm).
Does a softener add salt to my water?
It adds sodium. Penn State Extension says the exchange adds 7.5 milligrams per quart for each gpg of hardness removed, which matters for people on low-sodium diets. Ask your doctor if that applies to you.
Can a softener remove iron?
Colorless, dissolved iron, yes, up to a point. Penn State Extension says red, oxidized iron clogs the resin, so filter it out before the softener.