Uses of Water.—Water is a prime necessity of life. In its absence life can only exist in lowly organised beings, and in them only in a dormant state. From a hygienic point of view, the uses of water are four-fold:—(1) It is an essential part of our food, not only serving to build up the tissues of the body, but also preserving the fluidity of the blood and aiding excretion of effete matters. (2) It is necessary for personal cleanliness, of which the importance can scarcely be exaggerated. (3) In the household it is essential for cooking, as well as for washing the house, the linen, and various utensils. (4) By the community at large it is required for water-closets and sewers, for public baths, for cleansing the streets, and for horses and other domestic animals, as well as in many manufacturing processes. It is obvious that the water to be used for domestic and general purposes, need not be so pure as that for drinking purposes. Hence, a double supply was proposed for London in 1878, by the Metropolitan Board of Works—a less pure river supply for general purposes, and a deep chalk-well supply for drinking purposes. The scheme, however, rightly fell through, because of the expense of a double source of supply, and the danger that the impure water would, through carelessness or ignorance, be often used for drinking purposes, when it happened to be nearest at hand.
Quantity of Water Required.—The quantity of water required for all purposes has been variously stated by different authorities. The quantity required for drinking purposes is found to bear a relation to the weight of the individual, being nearly half an ounce for every pound weight, or 1½ gills for every stone weight. Thus, a man weighing 150 lbs. would require 3¾ pints. Of this water, about one-third is taken in the food; the remainder, averaging 2½ pints, being required as drink. If we add the water required for other purposes, according to De Chaumont, 1 gallon is required for drinking and cooking, 2 gallons (not including a bath) for personal cleanliness, 3 gallons for a share of utensil and house washing, 3 gallons for clothes washing; and if a general bath be taken, 3 gallons more; making a total of about 12 gallons, to which 5 gallons must be added if there is a water closet.
In hot summer weather the consumption is about 20 per cent. above the average of the year; and frost often increases the amount 30—40 per cent. above the average, owing to the bursting of pipes, or the loss from taps foolishly left open to prevent bursting.
Water companies usually reckon 30-60 gallons for each individual, to allow for the water required for scavenging and manufactories and for waste. In large houses and hotels where baths are freely used, often as much as 70 gallons per head is used, and in hospitals the amount averages from 60 to 90 gallons per head. The following is Parkes’ estimate of the daily allowance for all purposes:—
| GALLONS PER HEAD OF POPULATION. | |
|---|---|
| Domestic supply | 12 |
| General baths | 4 |
| Water-closets | 6 |
| Unavoidable waste | 3 |
| — | |
| Total house supply | 25 |
| Municipal purposes | 5 |
| Trade purposes | 5 |
| — | |
| Total | 35 |
It has been proposed to put a water-meter to each house, so that the rate may be in proportion to the amount of water used. The plan is objectionable for two reasons: 1st—Because it tends to restrict the necessary use of water for purposes of cleanliness. A scant supply of water is always followed by uncleanliness of house and person, with its consequent diseases; at the same time closets may be imperfectly flushed, and may become choked. 2nd—Because of the primary expense of the meter, and of its maintenance.
Sources of Water Supply.—All our drinking water is obtained in the first instance, by a natural process of distillation on a large scale. The sun is constantly causing evaporation from sea and land. The vapour produced, being condensed by a lower temperature, returns to the earth as snow, dew or rain. All these natural products have been at times utilised as sources of drinking water.
1. Dew has on rare occasions been utilised at sea by hanging out fleeces of wool at night and wringing them out in the morning. A much better plan is—
2. The Distillation of Sea-water. This can easily be managed now that steam power is so largely used. It has even been employed on land, when it was necessary temporarily to continue the use of water derived from an impure source. The first part distilled should always be rejected, as it is always impure. Distilled water is “flat” in taste, owing to its containing no dissolved gases. It can be aërated by letting it drop a considerable distance from one cask into another, through small openings in the upper one, and by filtration through charcoal. Non-aërated water is not easily absorbed into the circulation, and occasionally causes illness.
3. The utility of Melted Snow and Ice is obviously very limited. Moreover, its use is not free from danger if the ice is derived from contaminated water. Outbreaks of enteric fever have been traced in the United States to the taking of ice obtained from impure water.