Hard water is the most common water quality complaint in the US, and it’s also one of the least dangerous. Calcium and magnesium dissolved in water don’t make you sick. They do cause real, costly problems for your home.
The US Geological Survey estimates that 85% of US homes have hard water. If you’re in the Midwest, Southwest, or Florida, you almost certainly do.
What Hard Water Levels Mean
Hardness is typically reported in grains per gallon (gpg). One grain per gallon equals 17.1 mg/L of calcium carbonate.
The general scale:
- 0–1 gpg: Soft
- 1–7 gpg: Moderately hard
- 7–10 gpg: Hard
- 10+ gpg: Very hard
Phoenix, Arizona averages around 16–18 gpg. Indianapolis runs about 11–12 gpg. Seattle is usually under 1 gpg. Your utility’s Consumer Confidence Report will state your hardness, or you can get a test strip result in 30 seconds.
What Hard Water Does to Your Home
Scale — the chalky white mineral deposit — forms when hard water is heated or evaporates. Calcium carbonate precipitates out of solution and coats surfaces.
Inside your water heater, scale acts as insulation. A study by the Water Quality Research Foundation (2009) found that a water heater operating on 26 gpg hard water lost 47% efficiency after 15 years compared to one running on soft water. Scale buildup also reduces effective tank capacity and forces the heating element to work harder.
Dishwashers and washing machines accumulate scale in heating elements, pumps, and internal tubing. This accelerates wear. Industry estimates suggest water heaters in hard water areas last 8–12 years vs. 15+ years in soft water areas, though that range depends heavily on maintenance.
Showers and faucets develop calcium deposits around aerators and showerheads, restricting flow over time.
Soap reacts with calcium and magnesium to form soap scum — the insoluble residue on tubs, shower walls, and skin. Hard water requires more soap and detergent to achieve the same cleaning effect as soft water.
Testing for Hardness
An at-home test strip gives you a quick ballpark reading and costs almost nothing. For a more accurate measurement, a water test kit or a mail-in lab test will give you a precise gpg reading.
If your utility report shows your hardness, that reflects the water leaving the treatment plant. Hardness doesn’t change much between the plant and your tap, so the CCR number is usually reliable for treatment decisions.
Treatment Options
Ion exchange water softener. The only treatment method with consistent, independent test data behind it. A softener tank contains resin beads that attract and hold calcium and magnesium ions, releasing sodium ions into the water. Periodic regeneration with salt flushes the captured minerals down the drain and recharges the resin.
Result: water with very low hardness (typically under 1 gpg), significantly reduced scale, and better soap lathering. The water contains more sodium — an issue for people on low-sodium diets, though the sodium added per liter is modest at typical hardness levels.
Salt-free conditioners and template-assisted crystallization (TAC). These change the form of calcium carbonate — encouraging it to crystallize as aragonite rather than calcite. Aragonite is less likely to stick to surfaces. Independent research on TAC is limited but more favorable than for electronic descalers. The Water Quality Association acknowledges TAC as potentially effective for scale reduction in some conditions, while noting it doesn’t actually remove hardness minerals.
Reverse osmosis. An RO system will remove calcium and magnesium along with most other dissolved solids. If you already have an RO system for drinking water, your drinking water will be essentially mineral-free. But a point-of-use RO doesn’t treat water going to your water heater or dishwasher.
For the full comparison of softener vs. salt-free options: Water Softener vs. Salt-Free Conditioner