Understanding Water Hardness and Calcium
Water hardness is the traditional measure of the concentration of dissolved minerals, predominantly calcium ($Ca^{2+}$) and magnesium ($Mg^{2+}$) ions, present in water. As water flows through the ground and across rock formations, it naturally dissolves these minerals, carrying them into aquifers and, subsequently, into our water supplies. While the presence of these minerals is not typically considered a direct health risk, high concentrations can lead to numerous practical problems in a home. High calcium content is a primary contributor to this hardness.
Several organizations, including the United States Geological Survey (USGS) and the Water Quality Association (WQA), use standardized scales to classify water hardness based on the concentration of calcium carbonate ($CaCO_3$) equivalent, measured in milligrams per liter (mg/L) or parts per million (ppm), which are equivalent units. The following table summarizes a widely accepted classification scale.
Water Hardness Classification (as mg/L $CaCO_3$ equivalent)
| Classification | Concentration (mg/L) |
|---|---|
| Soft | 0–60 |
| Moderately Hard | 61–120 |
| Hard | 121–180 |
| Very Hard | >180 |
Based on these classifications, a high calcium concentration in drinking water generally starts when the total hardness exceeds 120 mg/L ($CaCO_3$). Extremely high levels are considered above 180 mg/L. It is important to note that the World Health Organization (WHO) has also set a taste threshold for calcium, which typically falls between 100–300 mg/L, suggesting that levels above this range may also be perceived as high simply due to taste.
Effects of High Calcium in Drinking Water
The effects of high calcium levels are often more of a nuisance than a direct health hazard, but they can still cause significant issues for homeowners.
Household and Aesthetic Impacts
- Limescale Buildup: This is one of the most visible signs of high calcium. As water with high mineral content is heated or left to evaporate, calcium carbonate precipitates out, forming a hard, white or off-white deposit called limescale. This scale can accumulate in kettles, coffee makers, and on faucets and showerheads.
- Plumbing Issues: Limescale can also build up inside pipes, particularly hot water pipes, reducing water flow and ultimately leading to clogs. This can decrease the lifespan of plumbing and water-using appliances, such as water heaters, washing machines, and dishwashers.
- Soap and Detergent Inefficiency: High calcium levels react with soap, preventing it from lathering properly. This results in the formation of a sticky, white soap scum. As a result, more soap, detergent, and cleaning agents are needed to achieve the same level of cleanliness, increasing household costs.
- Residue and Stains: Dishes and glassware can come out of the dishwasher with spots and a cloudy film. Laundry may appear dingy, and bathtub rings are common with hard water.
Health Considerations
- No Harmful Health Effects: The World Health Organization (WHO) and the U.S. Environmental Protection Agency (EPA) have stated that hard water is not known to have adverse health effects and is not a regulated contaminant. In fact, the calcium and magnesium in hard water can provide a small contribution to your overall dietary mineral intake.
- Skin and Hair Issues: For some people, particularly those with sensitive skin conditions like eczema, hard water can cause dryness and irritation. The mineral residue can leave hair feeling brittle and difficult to manage after washing.
- Gastrointestinal Discomfort: While uncommon, some individuals may experience gastrointestinal issues from high mineral intake, though the body typically regulates and excretes excess minerals effectively.
- Potential for Scaling in Kidneys: Studies have investigated links between hard water and health issues like kidney stones, but findings are often inconsistent or weak. Generally, adequate hydration and dietary factors are more significant in kidney stone formation.
How to Test and Treat Your Water for High Calcium
If you suspect you have hard water, there are several methods to confirm your calcium levels.
Testing Methods
- The Soap Test: A simple at-home test involves filling a clear bottle with tap water, adding a few drops of pure liquid soap, and shaking vigorously. If the water becomes cloudy and forms minimal bubbles, you likely have hard water.
- At-Home Test Kits: For a more precise measurement, test strips or liquid titration kits are available at hardware stores and online. These kits will provide a reading of your water's hardness in ppm or gpg.
- Professional Lab Analysis: For the most accurate results, especially for well water users, a certified laboratory can perform a detailed analysis. Your local municipality's water quality report can also provide data on hardness levels in your area.
Treatment Options
- Water Softeners: The most common and effective method to remove high calcium and magnesium is a water softener that uses an ion exchange process. The hard minerals are replaced with sodium or potassium ions. For individuals on a low-sodium diet, a potassium chloride system may be a suitable alternative.
- Reverse Osmosis (RO) Systems: These systems can be installed at the point of use to filter drinking and cooking water, removing dissolved minerals. However, they do not address the hardness problems for the entire household, such as in showers or laundry.
- Point-of-Use Filters: Some filters are designed to reduce hardness for specific purposes, such as filtered pitchers or faucet-mounted filters, but are less effective for whole-house treatment.
Conclusion
What is considered high calcium in drinking water is typically defined by standardized scales for water hardness, with levels above 120 mg/L ($CaCO_3$ equivalent) often categorized as hard and above 180 mg/L as very hard. While these elevated mineral levels are not a health hazard for most people, they cause a host of aesthetic and practical issues in the home, including limescale buildup, appliance damage, and reduced soap efficiency. By using a simple at-home test or professional analysis, homeowners can determine their water's hardness and choose an appropriate treatment method, such as a water softener, to protect their plumbing and improve their quality of life. WHO Hardness in Drinking Water Guideline
