The usual sources, in their relative order of purity, are: deep springs and land or surface springs, located either above or below the house, but not too near to settlements; deep subterranean water, made available by boring or drilling a well; upland or mountain brooks from uninhabited regions; underground water in places not populated, reached by a dug or driven well; lake water; rain water; surface water from cultivated fields; pond and river water; and finally, least desirable of all, shallow well water in villages or towns. These various sources of supply will be considered farther on. _An Ample Volume Necessary_ The second essential requirement is _ample quantity_. The supply must be one which furnishes an ample volume _at all seasons_ and for all purposes. What is a reasonable daily domestic consumption? The answer to this question necessarily depends upon the character of the building and the habits and occupation of its inmates. It is a universal experience that as soon as water is introduced it is used more lavishly, but also more recklessly and regardless of waste. For personal use, from twenty to twenty-five gallons per person should prove to be ample per day: this comprises water for drinking and cooking, for washing clothes, house and kitchen utensils, personal ablutions, and bathing; but, taking into account other requirements on the farm or of country houses, we require at least sixty gallons per capita per diem. To provide water for the horses, cows, sheep, for carriage washing, for the garden, for irrigation of the lawn, for fountains, etc., and keep a suitable reserve in case of fire, the supply should be not less than 150 gallons per person per day. _A Good Pressure Required_ The third essential requirement is a _good water pressure_. Where a suitable source of water is found, it pays to make it conveniently available, so as to avoid carrying water by hand, which is troublesome and not conducive to cleanliness. A sufficient pressure is attained by either storing water at, or lifting it to, a suitable elevation above the point of consumption. In this respect many farm and country houses are found to be but very imperfectly supplied. Often the tank is placed only slightly higher than the second story of the house. As a result, the water flows sluggishly at the bathroom faucets, and, in case of fire, no effective fire stream can be thrown. Where a reservoir is suitably located above the house, the pressure is sometimes lost by laying pipes too small in diameter to furnish an ample stream. Elevated tanks should always be placed so high as to afford a good working pressure in the entire system of pipes. Where a tower of the required height is objectionable, either on account of the cost or on account of appearance, pressure tanks may be installed which have many advantages.