A water softener
Investment and its drawbacks

One water softener Based on ion exchange, it provides soft water for a household and its appliances. Decalcifying drinking water reduces the degree of hardness. This leads to so-called water softening. The benefits: Less calcification and protects the lifespan of household appliances. What many do not know, however, is that such softening systems or Descaling systems Salt also has disadvantages. Before purchasing a water softening system, it is therefore useful to know these disadvantages. The following text clearly explains the disadvantages of a water softening system and what alternative there is for residents of the house.

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Water softening system — disadvantages summarized in a nutshell

• Extraction of the minerals calcium and magnesium from drinking water
• Water softening with salt increases the sodium level in drinking water
• Risk of contamination of drinking water during extended downtimes
• Increasing the metal aggressiveness of water and thus increasing the risk of corrosion
• A descaling plant with salt pollutes the environment due to chloride in the waste water
• Increased water consumption due to regeneration processes
• Current costs due to salt consumption and maintenance

Water softening system Disadvantage #1: Effects on drinking water quality: Minerals out — sodium in

A water softening system based on ion exchange leads to a change in drinking water quality as fed in by local drinking water supply companies. The water hardness or lime in water consists largely of the minerals calcium and magnesium. Hard water contains a particularly large number of these minerals. A softening system exchanges these calcium and magnesium ions for sodium. This results in an increase in the sodium level. This is also the reason why salt must be regularly refilled into the water softener's storage tank. From a nutritional point of view, this removal of minerals from drinking water may be undesirable (1). Especially when buying mineral water, the quality of the respective mineral water is often referred to with terms such as “rich in magnesium and calcium” or “low in sodium — suitable for preparing baby food.” However, an ion exchanger results in the opposite drinking water quality. The increase in sodium levels due to the use of a softener deserves special attention when the water is subsequently used to prepare infant formula. If the original water hardness or sodium value in the water is already very high, the sodium limit of 200 mg/l may also be exceeded in accordance with the Drinking Water Ordinance (2).

Water softening system Disadvantage #2: no lime, but rust in the drinking water installation

Soft or softened water not only has advantages. Softening systems using ion exchange have the disadvantage that they lead to a fundamental change in the corrosion-chemical behavior of water, as a result of which the water can have a metal aggressive effect. This is due to the fact that water softening systems disturb the so-called lime-carbonic acid balance of tap water. The use of water softening systems produces “excess” carbonic acid, which can attack the metal of household appliances and water pipes in the long term and can therefore cause damage to a drinking water installation, e.g. due to pitting. To prevent this metal aggressiveness, the water in a softening system is usually “blended” with untreated water and sometimes even post-treated with so-called inhibitors (such as phosphates). In this context, it is pointed out that inadequate post-treatment of soft water is the most common cause of corrosion damage in households with water softening systems. (3)

Water softening system Disadvantage #3: Risk of bacteria in drinking water due to a water softening system

Another disadvantage of a water softener or descaling system with salt is the risk of contamination of tap water. If drinking water stays in the ion exchanger resin for a longer period of time, an increased bacterial load must be expected. In systems with a longer service life, care should therefore be taken to disinfect this resin when the ion exchange resin of a softening system is regenerated (4).

Water softening system Disadvantage #4: Chloride in the waste water of a water softener system damages the environment

Softening systems not only have technical disadvantages, but also environmental disadvantages. Through the use of ion exchangers, high amounts of sodium and chloride get into the waste water. As a result, chloride pollution in a supply area can significantly increase (5). Due to the solubility of chlorine in water, the amounts of chlorine cannot be removed by municipal sewage treatment plants (6). The result would be a steady increase in chlorine pollution in water bodies.

In response to a question from MP Hendrik Lange about chlorine pollution in German waters, the state government of Sachen-Anhalt responded in 2016: “If there are deviations, sensitive species will fail, robust species will spread. The entire species and abundance structure of a community can change as a result (7). For this reason, in California, for example, due to excessive chloride levels in wastewater, there is already a law (Senate Bill 475) (8) that allows local authorities to prohibit the use of certain ion exchangers for private purposes (9).

Water softening system Disadvantage #5: increased water consumption due to regeneration processes

Another disadvantage of a descaling system with salt (ion exchanger) is the additional water consumption for regeneration processes. Depending on its size, a water softener can only soften a certain amount of drinking water at a time. Once this amount has been reached, it must be regenerated. This means that the ion exchange resin is rinsed with water at certain intervals and “loaded” with new sodium chloride solution. Many liters of water are required for this process. For a single-family house with three to four people, which is located in a region with hard water, this can in some cases mean an additional annual water consumption of up to several thousand liters of water.