Generally, the water temperature for brewing Pu'er tea should be above 90°C, so that the tea's aroma and flavor become more pronounced. Therefore, many people repeatedly boil the water each time they brew tea, or even keep the kettle boiling continuously, creating a misty effect. However, this is not advisable. Repeatedly boiled water contains a large amount of precipitated salts, which form white floating residues in the water.

During the boiling process, water continuously evaporates, increasing the concentration of salts with each boil. These insoluble salts have a poor taste, and some may even react with tea leaves components, affecting the tea's flavor. Trace metals like copper and iron also increase in repeatedly boiled water, reacting with tea polyphenols—the active components of tea—and diminishing its aroma. Furthermore, repeatedly boiled water contains nitrites, which can form carcinogenic nitrosamines in the body.

Recommendation: Boil only the necessary amount of water based on the number of tea drinkers, and after one round of brewing, refill with cold water and boil again.