I don’t generally worry about the safety of the water I drink. That wasn’t always true a hundred years ago. Here’s an abridged version of what a home economics textbook from the early 1900’s had to say:
Pure water is the most important of our foods. Water may contain impurities that come from decaying vegetable or animal matter, or it may carry the germs of disease, or minute insects or their eggs. Where shallow wells are used, water may wash filth into them. In deep wells, properly protected from insects and animals by high curbs, the water is usually pure because the many layers of soil, gravel, and rock through which it has filtered have taken out the impurities.
Even apparently pure water may contain germs only visible under the microscope. If there is any questions as to the purity of the water, send a sample to the state health laboratory or to a chemist for analysis.
If water is muddy let it settle, then pour off the clear water and boil it hard for five minutes. Put it into clean glass jars or bottles, cover it, and keep it cool. Boiled water is flat because the air is driven off, and may be aerated by being poured from a pitcher held at some height into a drinking receptacle. Distilled water, if bottled under clean conditions, is very useful in times of typhoid or epidemics of like nature.
The Science of Home Making: A Textbook in Home Economics (1915) by Emma E. Pirie