What are soft water and hard water? From a scientific perspective, water hardness is determined by the presence of compounds containing calcium and magnesium (expressed in milligrams per litre of water, or ppm). The higher the concentration of these compounds, particularly calcium carbonate (CaCO3), the harder the water. Water hardness is generally classified into four levels:
- Soft water: 0-60 ppm
- Moderately hard water: 60-120 ppm
- Hard water: 120-180 ppm
- Very hard water: 181 ppm and above
If we refer to the “Taiwan Area Water Hardness Overview” provided by Taiwan Water Corporation, we can observe significant variations in water hardness across different regions of Taiwan due to geological and hydrological conditions.
Region—————————Hardness
Taipei City———————Average below 50 ppm
Taipei County (Wugu, Taishan)—Around 150 ppm
Wugu, Taishan—————150-250 ppm
Longtan————————Around 100 ppm
Hsinchu, Miaoli————-180-200 ppm
Zhudong————————110-160 ppm
Central Taiwan (excluding Puli)—Above 180 ppm
Puli, Yuanlin, Beidou, Tianzhong—Below 100 ppm
Yunlin, Chiayi (excluding Alishan)—50-350 ppm
Tainan——————————-Around 300 ppm
Kaohsiung-Pingtung Area———150-300 ppm
Yilan———————————Below 150 ppm
Hualien——————————-Around 100 ppm
Taitung——————————-150-250 ppm
We currently cannot determine whether water is hard or soft simply by its colour or smell. However, we can observe certain phenomena: if you boil water and find a white, slightly slippery layer of scale (commonly known as ‘tea scum’ in Taiwanese), then it is hard water. Also, if you stir soap water and notice fewer bubbles, it indicates hard water.
Calcium and magnesium are essential trace elements for the human body, which must be obtained daily from diet. The health implications of the levels of calcium and magnesium ions in water are still uncertain. Some unscrupulous businesses mislead the public by claiming that high water hardness leads to kidney stones, which is unfounded. However, the government does regulate the drinking water quality with a standard upper limit of 300 mg/l of CaCO3 for total hardness.
Regardless of whether water hardness affects health, it does cause some inconvenience in daily life if water is hard. For instance, scale can affect the efficiency of water heaters, create stubborn white spots on chrome-plated bathroom fixtures and mirrors, and increase soap consumption and make fabrics stiff when used for laundry. On the other hand, soft water can accelerate pipe corrosion.
As for how to improve water hardness, we will discuss this in the next article!
Mentioning the use of filtration to remove limescale and achieve soft water effects, the most common filter medium is ion exchange resin.
Ion exchange” refers to: as water passes through the filter core, substances within the resin undergo billions of exchanges with minerals in the water. Metal cations such as calcium, magnesium, and aluminium are adsorbed onto the resin and sodium ions are released. After filtration, the content of calcium, magnesium, and other substances in the water decreases. When the resin’s adsorption capacity is saturated, it is immersed in sodium (salt water). During immersion, the previously adsorbed calcium and magnesium are released, while sodium ions are adsorbed. The chemical formula is as follows: (No need to memorise, it won’t be tested by the teacher)
Ca2++2Na-R→Ca-R2+2Na+1
Mg2++2Na-R→Mg-R2+2Na+1
Strictly speaking, water softeners that use ion exchange resin as the filter medium should not be referred to as “water purification devices,” as they do not remove pollutants from the water but merely reduce scale by removing calcium and magnesium ions. However, other contaminants in the water, such as organic pollutants, microorganisms, and suspended particles, cannot be filtered out. Therefore, ion exchange resins are only suitable for use as a pre-filter in water purifiers and cannot guarantee the purity of the water when used alone.
Generally, the lifespan of ion exchange resin is limited, typically around 2-3 months (depending on water quality). Some water filter jugs claim to add ion exchange resin to remove scale, but due to their small size, their lifespan is usually shorter. Therefore, one should not be overly optimistic about their effectiveness in removing scale.
Apart from their short lifespan and relatively high cost, the drawbacks of ion exchange resin filters include the release of sodium ions during the ion exchange process, which poses a health risk to kidney patients. Sodium-free ion exchange resin is also available, but the water filtered by sodium-free resin tends to be slightly acidic due to the release of hydrogen ions, depending on the consumer’s choice.
In addition to ion exchange resin, using RO water purification equipment is also an excellent option. The principle is that water molecules pass through the tiny pores of the RO membrane, which are one five-thousandth the diameter of a human hair, to filter out heavy metal ions, organic toxins, and bacteria. However, the downside is that the water passing through the reverse osmosis treatment produces waste water, potentially wasting water resources.
No water filtration method is 100% perfect; it depends on the consumer’s needs and preferences. Additionally, choosing a reputable brand with excellent product quality is essential for purchasing a water purifier. Easywell Water Purifiers, awarded the Ministry of Economic Affairs’ Little Giant Award, have achieved outstanding export performance with Taiwan-made water purification products, earning this honour and deserving the trust of the public.
