The first essential requirement is that of _wholesomeness_. The quality of a water supply is dependent upon physical properties and upon chemical and bacteriological characteristics. Water, to be suitable for drinking, must be neither too hard nor too soft; it should not contain too many suspended impurities, nor too much foreign matter in solution. Pure water is colorless and without odor. But it must be understood that the quality cannot be decided merely by the color, appearance, taste, and odor. The chemical and bacteriological examinations, if taken together, form a much safer guide, and with these analyses should go hand in hand a detailed survey of the water source and its surroundings. _Relation of Water to Health_ Any pronounced taste in the water renders it suspicious; an offensive smell points to organic contamination; turbidity indicates presence of suspended impurities, which may be either mineral or organic. But even bright and sparkling waters having a very good taste are sometimes found to be highly polluted. Hence, it should be remembered that neither bright appearance nor lack of bad taste warrants the belief that water is free from dangerous contamination. It is a well-established fact now that there is a relation between the character of the water supply and the health of a community; and what is true of cities, villages, and towns, is, of course, equally true of the individual country house. _How Water Becomes Contaminated_ There are numerous ways in which water may become polluted, either at the source or during storage or finally during distribution. Rain water, falling pure from the clouds, encounters dust, soot, decaying leaves and other vegetable matters, and ordure of birds on the roofs; its quality is also affected by the roofing material, or else it is contaminated in the cisterns by leakage from drains or cesspools. Upland waters contain generally vegetable matter, while surface water from cultivated lands becomes polluted by animal manure. River water becomes befouled by the discharge into it of the sewers from settlements and towns located on its banks. Subsoil water is liable to infiltration of solid and liquid wastes emanating from the human system, from leaky drains, sewers, or cesspools, stables, or farmyards; and even deep well water may become contaminated by reason of defects in the construction of the well. During storage, water becomes contaminated in open reservoirs by atmospheric impurities; a growth of vegetable organisms or algae often causes trouble, bad taste, or odor; water in open house tanks and in cisterns is also liable to pollution. During distribution, water may become changed in quality, owing to the action of the water on the material of the pipes. From what source shall good water be obtained? This is the problem which confronts many of those who decide to build in the country.