Chinese people deeply revered Luh Yu as the Saint of Tea (竧) because of his book, Cha Ching (竒), was the first publication on tea and way of tea. Although his book is dated more than a thousand years ago, his insights on tea still hold true to this day. He devoted his life in search of the best way to produce a perfect cup of tea by visiting various tea mountains and making meticulous observations on tea horticulture, teaware, tea tools, processing procedures, terroir, and cooking methods.
In his book, Luh Yu acknowledged the importance of water quality in tea preparation. His conclusions on water are based upon two factors - the impact on tea drinkers' health and the impact on tea's taste. He classified water into three categories: 1) from the mountain 2) from the river 3) from the well. Water gathered from the mountain is best suited for tea making whereas water gathered from the well is least desirable.
Furthermore, Luh Yu classified mountain water into two subcategories: rapid waterfalls and slow moving mountain streams or creeks. Luh Yu claimed that if one consumes water gathered from the rapid waterfall region for an extended period of time, neck ailment would develop. He suggested that one must survey the surrounding site and make wise decisions on water quality. Some streams are quite stagnant. Dragons or some other creatures may be dwelling in the water and releasing toxic matters. In these cases, do purify the water as one sees fit. Fetching river water is equally laborious to some people due to the distance they need to trek. And therefore, it is common to have people fetch water from their nearby well. It is a matter of personal preference; whether they want the most convenient source, or whether they want to put in the extra effort and trek to the best water source.
From today's point of view, ancient well water is the equivalent of our tap water. However, our bottled spring water is not necessarily the equivalent of their mountain water. With problems like pollution and land development, mountain water found in nature may require multiple filtrations before it can be used for drinking or tea making.