I drank softened salt water for three years because the water purifier was connected to the wrong water pipe. What harm does this do to my body?

Real points:

There is no big difference between softening salt and ordinary table salt, so softened water itself is safe. However, the harder the tap water, the more salty the softened water will taste, and such water is not suitable for drinking.

Verifier: Sun Yafei | PhD student in chemistry at Tsinghua University, member of the China Science Writers Association

Recently, a family in Hubei encountered a troublesome problem. They installed a whole-house water purification device at home, but they never expected that the water pipe of the water purifier was connected incorrectly - it should have been connected to the softened water in the bathroom, but it was connected to the kitchen. The family's kitchen water turned out to be softened water, and they have been drinking it for three years.

Over the years, with the popularity of water purifiers, "softened water" is not new to many people. But what exactly is softened water? Can you drink it?

1. In areas with hard water, it is recommended to use softened water in the bathroom at home

In the whole-house water purification system, two lines are generally designed. One line is used for washing clothes, bathing, or flushing the toilet. In layman's terms, it is non-drinking water, and softened water is used here; the other line is mainly for areas outside the bathroom, such as the kitchen, which is drinkable water.

In principle, softened water cannot be drunk, but what are the dangers of drinking it? This is related to the composition of tap water.

After being treated by the water plant, the composition of tap water is relatively simple. The main impurities are residual chlorine and some minerals, especially calcium and magnesium ions. In addition, there are a small amount of metal ions such as iron and zinc, and there may be some organic impurities. Of course, the content of these impurities varies depending on the water source. The so-called hard water and soft water are actually distinguished by the calcium and magnesium ions in the water. Hard water has a high concentration of calcium and magnesium ions, and soft water has a low concentration. Relatively speaking, the water quality in northern China is harder.

Hard water may cause inconvenience when washing clothes or taking a bath. This is because the solubility of calcium and magnesium ions decreases after being heated, and they are more likely to become precipitates. Therefore, when ordinary tap water is used to boil water for bathing, it is easy to form scale, and in serious cases, it will clog the shower or pipes. When washing clothes with soap or stearic acid series laundry detergent, the calcium and magnesium ions in the water will also form white precipitates with stearic acid, resulting in not only a waste of soap, but also white spots on the washed clothes.

Therefore, if the water in your area is too hard, you can use softened water in your home bathroom.

2. Softening salt is no different from ordinary table salt, and softened water is also safe, but if it is too salty, it is not suitable for drinking

The principle of softening water is very simple, that is, let the water pass through ion exchange resins. There are many sodium ions on these resins. When hard water passes through, calcium ions will be adsorbed by the resin and exchanged for sodium ions into the water. Sodium ions are somewhat salty, so softened water may also have a little salty taste because it is equivalent to diluted salt water.

Of course, after using the ion exchange resin for a long time, the sodium ions on it will eventually be exchanged out. At this time, the resin needs to be soaked in very concentrated salt water, and the calcium and magnesium adsorbed on the resin will be re-eluted by the sodium ions in the salt. The salt used here is generally "softening salt" provided by the manufacturer. In fact, there is no big difference between softening salt and ordinary table salt, and it is even purer than ordinary table salt. However, in terms of use, this salt is still industrial salt, so the manufacturer will mark "Do not eat" on its outer packaging.

The harder the tap water is, the more salty the softened water will be, and such water is not suitable for drinking. For most people, it is very easy to get salt from their diet, and they often even exceed the standard, so doctors always emphasize the need to control salt during physical examinations. On the contrary, for the elderly and children, calcium and magnesium ions are more likely to be deficient. The "Health Risks of Drinking Purified Water" published by the World Health Organization in 2019 pointed out that although drinking water is not the main source of calcium and magnesium ions, its health significance cannot be ignored. So in general, drinking softened water is not as good for health as drinking tap water directly.

Of course, it doesn't mean that hard water is necessarily good. Although hard water can provide some calcium and magnesium ions, it is easy to produce scale when boiling water and foam when making tea, which is also a very annoying phenomenon. Especially in some areas in the north, the water quality is too hard, and the concentration of calcium and magnesium ions is too high, which makes the water taste bitter and unpleasant.

The current popular whole-house water purification solution is to use ultrafiltration or reverse osmosis technology to treat water into very pure water, whether it is calcium, magnesium or sodium ions, all are removed. This pure water is connected to the kitchen and can be drunk directly.

3. There is a possibility that the water pipe of the water purifier is connected incorrectly. You need to confirm whether it is installed correctly before use.

In fact, for adults, the problem in this case in Hubei is not serious. It is nothing more than eating a little more salt. The maximum amount of extra intake per day is about 1 gram. However, from the report, we know that the person in question has three babies at home and has been using softened water to make milk powder. Children's bodies are still developing, and excessive intake of salt may damage the kidneys. In this case, it is best to go to the hospital for examination.

If this incident was indeed caused by the operator connecting the water pipe incorrectly, it is actually a low-level mistake, but it does happen in reality, because many filter elements are currently imported products, and the Chinese instructions are not very clear, so the operator may be careless. Therefore, when installing water purification equipment at home, be sure to find a reliable manufacturer and professional installer to install it, and repeatedly confirm whether it is installed correctly.

Editor of this article: ambergchen