Water Quality | What is hardness in water?

Water described as “hard” contains high amounts of naturally occurring dissolved calcium and magnesium. Total hardness is the sum of the calcium and magnesium concentrations, both expressed as calcium carbonate, in milligrams per liter (mg/L). You can determine your water’s hardness based on these concentrations of calcium carbonate:

below 75 mg/L - is generally considered soft

76 to 150 mg/L - moderately hard

151 to 300 mg/L - hard

more than 300 mg/ - very hard

Hardness in water can indicate high concentrations of calcium, magnesium and other dissolved minerals. In general, this includes 120-180 ppm of iron, calcium and magnesium, or at least 61 milligrams per liter or higher of calcium carbonate concentration. While magnesium and calcium are essential for our health and wellbeing, high amounts of these minerals in your tap water can cause a number of problems around your home. From cooking to cleaning, water is an important aspect of everyday life. While you may not feel the effects of drinking hard water, you may notice the impact it has on your home. Over time, hardness in your working water can cause damage to water-using appliances, including your washing machine, dishwasher and hot water heater, as well as fixtures and drains.

Hard water (high in calcium and magnesium) is not a health risk. The calcium and magnesium in water can contribute positively to your overall mineral intake. An 8-ounce glass of moderately hard water contains about 50 to 75 mg of calcium. In comparison, an 8-ounce glass of milk provides about 300 mg of calcium.

Hard water can also be a nuisance at home because of:

Gray staining of washed clothes

Scum on wash and bath water after using soap or detergent

Reduced lathering of soaps

Buildup of scale on heating elements and boilers

Reduced water flow in hot water distribution pipes due to scale buildup

Accumulation of whitish-gray scale in tea kettles and other containers used to boil water

Hardness minerals can be removed with a water softener, which replaces the calcium and magnesium (and iron, manganese, radium and other positive ions) with sodium. High levels of sodium in drinking water may harm your health.

People who have high blood pressure or are on a sodium-restricted diet should not drink water containing greater than 20 mg/L of sodium without first checking with a health care professional. If you are concerned about your sodium intake but would like soft water for your appliances and plumbing, you can have your kitchen cold water faucet bypass the water softener.

Water Softeners

The most common way to remove hardness from drinking water is to install a water softener, which replaces the calcium and magnesium ions with sodium ions. For every milligram of hardness that is removed, 0.46 milligrams of sodium will be added to the water. Potassium chloride can be used as an alternative to sodium chloride, but potassium chloride is not as efficient at removing hardness.

Consider the location of nearby water sources before disposing of the wastewater produced by a water softener. The wastewater could contaminate nearby wells with sodium, so underground disposal should take place downhill and as far as possible from the well.

Hard water can cause scale on reverse osmosis treatment membranes and ultraviolet light bulbs, which can make treatment less effective. A water softener can resolve this problem.

The membrane manufacturers will often specify what the maximum hardness concentration can be, but industry rule of thumb is that hardness should not exceed 120 to 170 mg/L (7 to 10 grains per gallon).

Does TDSBot measure hardness of water? 

No, as it measures the Total Dissolved solids, not just Calcium and Magnesium. To test hardness one needs to get a special kit to do it.