Water Hardness

What is water hardness?

Hardness is the measure of calcium carbonate in water, measured in milligrams per litre (mg/L). Hardness levels depend on mineral deposits (i.e. rocks and soils) from the catchment that supply our water.

Difference between hard and soft water

Hard water is water that has a high mineral content. The quickest way to work out whether your water is hard is to try to lather soap. If it doesn’t lather up, your water is hard. If it lathers extremely easily, then it is soft. The Australian Drinking Water Guidelines (2011) have a scale (see below) of water hardness as it impacts on water quality.

Westernport Water’s supply ranges from 50-120 mg/L with a median result over the last 7 years of 93 mg/L – which is considered as ‘good quality’ under the Australian Drinking Water Guidelines

LevelDescription
Less than 60 mg/L
Soft but possibly corrosive
60-200 mg/LGood quality
200-500 mg/LIncreasing scaling problems
>500mg/LSevere scaling

What does this mean for my tap water?

When hard water is heated, the minerals that cause hardness come out of the water and are deposited as scale. This can affect kettles, hot water services, pipes and fittings. Scale is harmless, but over time it builds up.

The most common way to reduce the build up of scale is keeping hot water systems below 60 degrees Celsius. Some uncommon methods are installing a water softener to bring to an unacceptable level. However results show that Westernport Water’s supply is in a good quality range therefore we do not recommend you drink softened water. Softeners can significantly increase the level of salt in your water.

Some dishwashers have settings that control the addition of salt, which acts like a water softener and decreases the build-up of scale. Generally dishwashers quote a quality range of water in mmol/L. To convert the measurement from mg/L to mmol/L for dishwasher references you simply divide by 100. Therefore the range of Westernport Water’s supply in mmol/L is 0.5-1.2 and for the median, 0.93 mmol/L