Many people use tap water directly when decocting Chinese herbal medicine, but this is not advisable.
Before tap water reaches homes, it undergoes purification and disinfection at the water treatment plant, which involves adding a certain amount of bleaching powder (mainly calcium hypochlorite) to achieve the purpose of sterilization. Chlorine is a strong oxidant that can react with many organic substances. If such tap water is used to decoct Chinese medicine, it will inevitably affect its organic components, reducing the medicinal efficacy.
So, how can the residual chlorine in tap water be removed? The simplest and most effective method is to boil the water. During the heating and boiling process, most of the residual chlorine will evaporate. To minimize the residual chlorine in the water, it is best to continue boiling for another 3-5 minutes after the water comes to a boil, and do not cover the pot (to facilitate the volatilization of chlorine). At the same time, during the heating process, carbonates such as calcium and magnesium in the water decompose and precipitate, reducing the content of calcium and magnesium ions. This also reduces the chance of effective ingredients in the herbs combining with calcium and magnesium ions to form precipitates, thereby enhancing the medicinal efficacy.
It should be noted that you cannot use water that has just been boiled to decoct the medicine. Otherwise, the starch, protein, and other components on the surface of the Chinese herbal pieces will denature or coagulate due to sudden heating, which is not conducive to the extraction of effective ingredients from the herbs and affects the medicinal efficacy.
The correct method is to boil the water, let it cool to room temperature, and then add the herbs. The amount of water added should generally be about 2-3 centimeters above the surface of the herbs. For the second decoction, you can use water that has just been boiled, which can also reduce the decoction time.