Understanding Water Hardness: Effects on people, plant and equipment
What Is Water Hardness?
Water hardness refers to the concentration of dissolved minerals, primarily calcium and magnesium, in water. The more minerals present, the "harder" the water. Hard water occurs naturally as groundwater passes through limestone, chalk, and other mineral-rich deposits, picking up these elements along the way.
Signs of Hard Water: How to Determine If Your Water Is Hard
Identifying hard water is essential to prevent damage to appliances, equipment, plumbing and pipework. Common signs of hard water include:
White, chalky residue on taps and showerheads. This residue is limescale.
Soap and shampoo not lathering well
Stiff or rough-feeling laundry after washing
Spotting on glassware after washing
Dry skin and dull hair after showering
Testing for Hard Water
There are various tests available that will give an indication of the hardness of water. These include:
Soap Test: A simple at-home test that anyone can perform using liquid soap. If the water doesn’t form suds easily, it is likely hard.
Hard Water Test Strips: Widely available online and from your local hardware store, these strips change color based on water hardness levels. These will give you an idea of how hard your water is.
Total Dissolved Solids (TDS) Meters: A Total Dissolved Solids Meter is a hand held electronic device that measures the concentration of dissolved minerals in water. It is worth noting that a TDS meter measures only the concentration of total dissolved solids, it does not tell you what those dissolved solids are. If you need to know what the dissolved solids are, then you will need to carry out a laboratory test.
Laboratory Testing: A professional, and consequently more expensive, water analysis provides the most accurate results and measures hardness in specific units, and will tell what dissolved solids are present in the sample analysed.
Units of Measurement for Water Hardness
The degree of water hardness can be expressed in various forms, including the following:
Parts Per Million (ppm): One part per million is defined as one milligram of calcium carbonate (CaCO3) per litre of water.
Milligrams Per Liter (mg/L): Equivalent to ppm. Tends to be used in scientific contexts.
Grains Per Gallon (GPG): Common in the USA. 1 grain (64.8 milligrams) of calcium carbonate dissolved in 1 US gallon of water (3.785412 L). 1 GPG equals 17.1 ppm.
Degrees of General Hardness (dGH) : 1 dGH is defined as 10 milligrams (mg) of calcium oxide (CaO) per litre of water. Since CaO has a molar mass of 56.08 g/mol, 1 dGH is equivalent to 0.17832 mmol per litre of elemental calcium and/or magnesium ions. 1 dGH corresponds to 10 ppm CaO but 17.848 ppm CaCO3 which has a molar mass of 100.09 g/mol.
Degrees Clark (°CI): A somewhat dated unit, once popular in the UK. 1 degree Clarke is 1 part of CaCO3 per 70,000 parts of water. One degree Clark is equal to the 14.3 ppm.
French Degree (°f): A somewhat dated unit, once popular in the France. One French degree is equal to 10 milligrams of calcium carbonate (CaCO3) per liter of water. One French degree is equal to 10 ppm. Note: lowercase f is used to prevent confusion with degrees Fahrenheit
German Degree (°dH): A somewhat dated unit, once popular in the Germany. A German degree (°dH, deutsche Härte) is defined as 10 milligrams of CaO per liter of water. One German degree is equal to 17.848 ppm.
What is Considered Hard Water
Soft: 0 – 50 ppm
Moderately Soft: 50 – 100 ppm
Slightly Hard: 100 – 150 ppm
Moderately Hard: 150 – 200 ppm
Hard: 200 – 300 ppm
Very Hard: over 300 ppm
Generally problems arise at levels greater than 200 ppm
Problems Caused by Hard Water
Hard water can lead to several issues, affecting homes, industries, and even human health. These include:
- Piping and Plumbing Damage can occur when mineral buildup, often referred to as scale, on the walls of the pipes leads to reduced water flow.
- Higher Energy Bills are encountered due to higher pump power required to maintain flow rates. Additionally, scale build-up reduces heating efficiency, leading to increased energy consumption in heat exchangers and water heaters.
- Cleaning Effectiveness is reduced when soap scum forms on surfaces, making it harder to clean clothes, dishes, and bathrooms.
How to Treat Hard Water and Make It Soft
Water softening is the process of removing excess minerals to improve water quality. The most effective treatments include:
Ion Exchange Water Softeners: Replace calcium and magnesium ions with sodium or potassium, softening the water.
Salt-Free Water Conditioners: These devices alter the mineral structure to prevent scale formation without removing minerals.
Reverse Osmosis (RO) Systems: Use a membrane to filter out minerals and other impurities.
Chelation Systems: Bind minerals to prevent them from forming scale deposits.
Electromagnetic or Magnetic Water Conditioners: These alter the physical properties of minerals to reduce scale formation, though their effectiveness is debated.
Instruments for Detecting Hard Water
Several instruments can measure and monitor water hardness levels:
Inline Water Hardness Monitors are common in industrial applications where they are nstalled in piping and plumbing systems to provide continuous (real-time) monitoring of mineral content in water, i.e. water hardness levels.
Test Strips are primarily used in domestic applications. These simple, disposable, small paper strips are chemically treated to indicate the level of dissolved minerals. The strips change color based on hardness levels.
Titration Kits are used by professionals, often in laboratory conditions to accurately determine water hardness by measuring the reaction of water with chemical reagents.
Conclusion
Understanding water hardness is crucial for maintaining piping and plumbing systems, household appliances, and personal hygiene. By recognising the signs of hard water, testing for hardness levels, and using effective treatment methods, homeowners and engineers can prevent costly damage and ensure high water quality.
Return to Technical Toolbox index
