The short answer
Hard water is water high in dissolved calcium and magnesium. The US Geological Survey says hardness isn’t a health concern, but it can be a nuisance: scale in pipes and water heaters, spots on dishes, and soap that won’t lather. A water softener certified to NSF/ANSI 44 removes hardness; drinking water filters and salt-free conditioners don’t.
What is hard water?
Hardness comes from calcium and magnesium the water picks up from rock and soil. The USGS classifies it by milligrams per liter as calcium carbonate; softener sellers often use grains per gallon, where one grain equals 17.1 mg/L.
| Classification | 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 |
| Hard | 121 to 180 | 7.1 to 10.5 |
| Very hard | Over 180 | Over 10.5 |
Grains per gallon are mg/L divided by 17.1. The USGS says hard water is most common in the east-central and western United States.
Is hard water bad for you?
No. The USGS says hardness isn’t a health concern, the EPA has no standard for it, and the World Health Organization proposes no guideline value because there are insufficient data to suggest minimum or maximum mineral levels. The WHO notes that a possible protective effect of magnesium or hardness on heart health is still debated and doesn’t prove causality.
What does hard water do to your home?
- Scale: Calcium carbonate deposits can shorten the life of equipment and lower the efficiency of electric water heaters.
- Soap: Hard water needs considerably more soap to lather, and soap reacts with calcium to form soap scum.
- Spots and buildup: On dishes, glass, faucets, and showerheads. See how to remove hard water stains.
How do you fix hard water?
Salt-based water softener. An ion exchange softener swaps calcium and magnesium for sodium (or potassium). NSF/ANSI 44 is the certification for these softeners. Softening adds sodium: Aquasana, which makes softeners, says it adds about 7.5 mg per quart for each grain of hardness removed, so some people keep an unsoftened tap for drinking or use potassium chloride.
Salt-free conditioners. These don’t remove hardness; they aim to reduce scale. IAPMO/ANSI Z601 now sets a test for scale-reduction devices, but few products carry it. NSF/ANSI 44 covers only salt-regenerated softeners.
Drinking water filters. Pitchers, carbon filters, and fridge filters aren’t certified to soften water. Reverse osmosis certified for dissolved solids lowers minerals at one tap, but it isn’t a whole-house fix.
Our softener picks are the Aquasana SimplySoft and the Kenmore 350, both certified to NSF/ANSI 44. Compare every option, including reverse osmosis for drinking water, in our best water filter for hard water guide.
Aquasana SimplySoft
Kenmore 350
SpringWell FutureSoft
How do you test for hard water?
Hardness test strips and kits are inexpensive and widely sold; a lab test is more accurate. On city water, your utility’s annual water quality report often lists hardness.
Tap Score Advanced Home Water Test
Common questions
Is hard water safe to drink?
Yes. The USGS says hardness isn’t a health concern, and the WHO sets no health-based guideline for it.
How many grains per gallon is hard water?
About 7 or more. The USGS classes water over 120 mg/L as hard, and 120 mg/L is about 7 grains per gallon at 17.1 mg/L per grain.
Do salt-free water softeners work?
They don’t remove hardness; they aim to reduce scale, and few carry any certification for it. A salt-based softener certified to NSF/ANSI 44, such as the Aquasana SimplySoft, removes it.
Does a water softener add sodium to my water?
Yes. Aquasana, which makes softeners, says it adds about 7.5 mg per quart for each grain of hardness removed. Ask your doctor if you’re on a sodium-restricted diet.
Does a Brita filter remove hardness?
No. Brita filters aren’t certified to reduce hardness. See what a Brita filters out.
Sources
Prices as of November 1, 2026. Product prices and availability are accurate as of the date/time indicated and are subject to change. As an Amazon Associate we earn from qualifying purchases.