Plain boiled water, also known as cool white water, is the alkaline water that people drink the most in daily life. It is light and tasteless, extremely common, but has a very important conditioning effect on the physiological mechanism of the human body. Drinking a glass of warm plain water on an empty stomach in the morning is good for the body without any harm.
The plain water is not suitable for drinking after more than three days. If the water is stored for too long, it will be infected by bacteria to produce nitrite.