What is Calcium & Magnesium (Hardness)?
The two most common elements that contribute to water hardness are calcium and magnesium. When these are found in water they leave a white powdery precipitate that is often called lime scale.
The New Zealand drinking water standards give a guideline value of <200mg/L. However it is important to note that the drinking water standards are concerned with drinking water rather than plumbing. Issues around the home are noted at much lower levels.
The World Health Organisation recognises the following levels for determining water hardness:
| Magnesium levels | Definition | Description |
| <60mg/L | Soft water | Little or no lime scale found |
| 60-120mg/L | Moderately hard | Lime scale noted particularly where water is heated |
| 120-180mg/L | Hard | Scale will form where hot or cold water comes into contact with fixtures |
| >180mg/L | Very hard | Severe scaling expected |
Where does hardness come from?
The hardness comes from limestone and sedimentary rocks which contain calcium and magnesium. As water passes over these rocks, the calcium and magnesium dissolve into the water.
What does hardness/limescale do?
Hardness means that water does not react with soaps and detergents as well as softener water. Soaps do not lather as well, they form an insoluble curd together and are the cause of ‘soap scum’.
When showering in hard water it can leave the hair flat and skin feeling dull. When doing laundry, it can often feel hard or scratchy and colours can dull.
When hardness precipitates from water (it does this faster at higher temperatures), it leaves behind a soft white deposit, which is very similar to the limestone it came from. This is often noted as water spotting on glasses, shower doors, taps, showerheads. The less noticeable issues are pipes slowly blocking reducing water flow, damage to dishwashers, washing machines, and hot water cylinders as hardness settles out in them.
Water heating is less efficient, as the hardness covers the elements, it essentially insulates them. This means that the element has to work harder and harder to get the water to the same temperature.
Hardness or silica?
Hardness can often be mistaken for another mineral called silica which causes very similar looking scale, however removing silica is very different to removing magnesium.
The best way to know whether you have hardness or silica is to get a water test.
How can I remove hardness?
Water softening is the most common, cost-effective method to remove hardness. Shop our range now to find a solution to suit your needs or chat to us for some expert advice.
