Hard water contains excessive levels of the minerals calcium and magnesium, a condition in 85 percent of Canada and the United States. Hard water leaves scale deposits that shorten the life of household plumbing and water-using appliances, make cleaning and laundering tasks more difficult and gradually decrease the efficiency of water heaters.
Water hardness is commonly measured in grains of hardness per US gallons of water or in milligrams per litre. At less than 1 grain per gallon, water is soft. Over 7 grains par gallon water is considered hard, over 10.5 grains per gallons is considered very hard.
| Hardness Rating | Grains per gallon (gpg) | Milligram per Litre (mg/L) |
| Soft | Less than 1.0 | Less than 17.1 |
| Slightly Hard | 1.0 to 3.5 | 17.1 to 60 |
| Moderately Hard | 3.5 to 7.0 | 60 to 120 |
| Hard | 7.0 to 10.5 | 120 to 180 |
| Very Hard | 10.5 and above | 180 and above |
Several municipalities across Canada have hard to extremely hard water. To put this in perspective, water in Toronto is considered moderately hard at 6 to 7 grains per gallon; water in the Guelph, Kitchener, Waterloo area hardness averages 34 grains per gallon, which is extremely hard. In Calgary, Red Deer and Edmonton water hardness averages 12 to 16 grains per gallon. By comparison, water in Vancouver is naturally soft at 0.3 grains per gallon.
Click here to see a list of water hardness by municipality compiled by CWQA. or look for your city or municipality most recently published water quality report. Most cities publish this information on their website.
A recent study by Battelle Memorial Institute, the world’s largest non-profit research and development organisation, measured the effects of hard water on water heaters specifically. Following a rigorous testing methodology, the Battelle testing was done on 26 grains per gallon hard water. It was found that:
- Gas storage tank water heaters operated on softened water maintained the original factory efficiency rating over a 15-year lifetime.
- Comparatively, gas storage tank water heaters operated on hard water lost as much as 24% of their efficiency. Specifically each 5 grains per gallon of hardness causes a 4% loss in efficiency and 4% increase in cost for gas storage tank water heaters when using 50 gallons of hot water per day.
- Each 5 grains per gallon of water hardness caused 0.4 pounds of scale accumulation each year in electric storage tank water heaters. As a result, the life of the heating element can be expected to shorten due to scale buildup increasing the operating temperature of the element.
- Tankless water heater operated on softened water maintained their original factory efficiency rating over a 15-year lifetime.
- Comparatively with hard water the study found that tankless water heaters completely failed to function because of scale plugging in the downstream plumbing after only 1.6 years of equivalent hot water use on 26 grains per gallon hard water.
The same study also looked at the effect on showerheads and plumbing fixtures. Showerheads on hard water lost 75% of the flow rate in less than 18 months. Showerheads on soft water maintained a brilliant luster and full flow.
Click here to view a summary of the Battelle Study.