What Exactly Is Water Hardness And How Bad Is It For You

by Curtis Grossi | Last Updated: March 19, 2024

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Some studies have pointed towards a weak inverse relationship between hardness of water and cardiovascular disease, while others have tended to show the opposite. The US National Research Council of the National Academy of Sciences has found that hard water can in fact contribute to the dietary needs for calcium and magnesium.

However, it has also stated that results are inconclusive and that further studies need to be conducted in order to determine recommended minimum and maximum levels of water hardness.

There is no evidence that hard water is harmful to human health, and most studies have failed to show any clear linkages for or against the health effects of consumption of hard water.

Trials were undertaken in 2008 to study the potential correlation between domestic hard water usage and the increased incidence of eczema in children, but no meaningful difference was found between users of soft and hard domestic water.

What is Hard Water?

Hard water is defined as water that contains high levels of ‘hardness’ minerals. Water that flows through limestone or dolomite rock formations before being drawn into the water supply will dissolve small portions of the rock it passes over, drawing calcium and magnesium ‘hardness’ ions into the water supply.

When the water is heated, such as in a household water heater (see on Amazon), the hardness ions will react with dissolved carbon dioxide in the water and with the water molecules themselves, to form calcium carbonate and magnesium carbonate deposits on the interior surfaces of the water infrastructure with which the hard water comes into contact.

These can include the household hot water piping system, water heating elements in the water heater and household kettles, and hot water faucets. The buildup of these deposits forms a scale or ‘lime-scale’ layer that reduces the efficiency of the items in which it forms, insulating heating elements and reducing pipe diameters.

Hard water also reduces the ability of soaps and detergents to form soapsuds and foam for removing dirt and grease from whatever they are being used to clean or wash. Instead, a ‘soap scum’ will form, which will require the addition of more soap to clean off. In addition, hardness ions can build up on surfaces that are subject to the hot water, such as shower doors and walls, and will require hard scrubbing to remove.

The US Geological Survey (USGS) classifies water with more than 7.05gpg (120ppm) of hardness minerals as ‘hard’, and water with more than 10.55gpg (180ppm) as ‘very hard’. The effects of hard water will begin to be noticeable at a hardness of about 7gpg (120ppm), but will become a nuisance that needs serious attention by 10.5gpg (180ppm).

How To Test For Hard Water?

Water hardness is determined by the sum of calcium and magnesium ions in a set volume of water, expressed as parts per million (ppm) or grains per gallon (gpg).

There are a number of ways to test for the level of hardness in your water, with varying degrees of accuracy. But before going to the trouble of purchasing a water hardness test kit, you should approach your local water supply utility for information on the hardness of the water that they supply.

If they are unable to provide an accurate reading for your area, or if you are on an independent water supply, such as well water in a rural area, you can either employ a water quality professional to test your water, or invest in a home water hardness test kit (buy at Amazon).

These come in a variety of forms and sizes, but it is important not to make the mistake of buying an aquarium test kit or swimming pool water test kit when you want to test the hardness of your household drinking water supply.

Also, note that ‘water purity’ kits do not measure water hardness, water safety, or the chemical or bacterial makeup of your water, but simply the quantity of particles in your water, whatever form they may take.

A further alternative, depending on where you are located, is to approach one of the large department stores, such as Sears & Roebuck, that offer free water testing to their customers.

These tests cover acidity, hardness and clarity. You can get a water sample bottle from them, fill it with water from your faucet, and return it for testing; or provide a sample of water from your faucet in a sterile bottle of your own.

If you need to or decide to test water hardness levels yourself, there are two main types of water hardness kit available. One is in the form of test strips, which will give you a general hardness reading in the range of 100ppm (6 grains) per gradation. The other is a titration test kit, which gives a more accurate measure of water hardness, within the range of about 10ppm (1/2 grain).

Good quality test strips will measure up to five different factors; free chlorine, total chlorine, total hardness, total alkalinity and pH. Since high chlorine levels lead to the breakdown of the resin in an ion-exchange water softener, it would be useful to know so that you can treat the resin or the water to reduce the effect of the chlorine.

Simply fill a clean glass with water from your household faucet, then insert a test strip for three to five seconds, and remove it. Don’t place the test strip under running water, and don’t flick the water drops off the test strip. After a few seconds the strip will change color. The color change on the strip can then be compared with the color chart included with the kit to give an indication of the water hardness, and other characteristics if available.

If you decide to rather opt for a titration test kit, you will find that the kit includes an empty container for testing the water as well as a small bottle containing an organic chelating solution, or ‘reagent’, which reacts with calcium and magnesium ions.

Fill the empty container with household faucet water to the level indicated and then carefully squeeze one drop at a time of the reagent into the water. As the reagent reacts with the calcium and magnesium ions in the water, the water will first turn red, then purple and, finally, blue. Once the blue color is reached, add another drop to ensure no further change in color, but don’t count that last drop when reading off the water hardness table.

The number of drops of the reagent required for the water to turn blue can be compared with a table supplied with the kit, to indicate the water hardness.

If the water stays purple, or if the blue color fades, then either there are other contaminants such as metal ions in the water, for which other measures or tests are required, or the reagent has spoiled (it should be protected from direct sunlight and temperature extremes).

Always handle the test equipment and the reagents with care, as the liquid can cause skin or eye irritation. If you experience any problems, it is advisable to seek professional assistance.

While the titration method will give a more accurate reading of water hardness levels if the water is uncontaminated, the test strips will give an indication of the levels of other minerals and chemicals.

How To Tell If You Have Hard Water?

Water hardness was at one time defined as a measure of water’s capacity to precipitate soap, and one of the easiest ways to determine if you have hard water is to fill a clear plastic bottle one-third full of household faucet water, then add a few drops of pure liquid soap, and shake the bottle for a few seconds.

Since many cleaning agents contain detergents to combat water hardness, the liquid soap must be a basic soap that is free from perfumes, dyes or detergents.

If, after being shaken, the bottle fills with bubbles and the remaining water is clear, then you have soft water, but if there are few bubbles and the water is cloudy, then your water is hard.

Other indicators of hard water include the following:

• Bathtub rings
• White spots on dishes and cutlery after washing
• Hard milky film on glass shower doors
• Soaps and shampoos don’t lather easily
• White crust accumulating around faucets, shower heads and drains
• Lime-scale encrusting the inside of your kettle
• Soap scum in sinks and bathtubs resulting in dry skin and possible skin infections.

Curtis is the founder and owner of softeningwater.com. He is the lead guy concerning all the water-softening accessories in this site's guides and reviews. If he is not writing a reviews, guides or any other useful tips, you will find him testing them to find out their suitability. He is passionate about softening water. You will find him extremely helpful and always willing to educate the general populace all there is concerning water and its effects on their health and appliances.