Rural Hygiene

by Henry N. Ogden

Again, in the hot weather of summer, more water is used for bathing and laundry purposes than in cold weather. But, on the other hand, there is a great tendency in cold weather to let the water run in a slow stream from faucets in order to prevent freezing. This has been found to just about double the amount of water used. It is only a reasonable safeguard, therefore, if it has been decided that the family needs are such as to require twenty-five gallons per head per day, to provide for double that amount in order to meet the demands of excessive daily consumption or of the hot and cold weather extremes.

Fire streams.

If a water-supply is to be installed for any house, the possibility of providing mains of sufficient size for adequate fire protection should always be considered, although it may not be found to be a necessary expenditure. In case of a fire a large amount of water is needed for a few hours, entirely negligible if it is computed as an average for the year, but a controlling factor in determining the size of mains or the amount of storage.

A good-sized fire stream delivers about 150 gallons per minute, and for a house in flames, four streams are none too many. The rate of delivery, therefore, for a fire should be at least 600 gallons per minute or a rate of nearly a million gallons per day, and if it is assumed that the fire might burn an hour before being extinguished, 36,000 gallons of water would be used. If a spring or tank is the source of supply, the storage should be 36,000 gallons, and the pipe line from the tank to the hydrants must be large enough to freely deliver water at the rate of 600 gallons per minute. If the distance is not over 500 feet, a four-inch pipe is sufficiently large; but if the distance involved (from the reservoir or tank to the farthest hydrant) is more than about 500 feet, four-inch pipe is not large enough. This is because the friction in a large line of pipe is so great that the water cannot get through in the desired quantity. A four-inch pipe, discharging 600 gallons a minute, would need a fall of one foot in every four feet, while a six-inch pipe would need a fall of only one in thirty. Of course, if the reservoir from which the water comes is at such an elevation that the greater fall is obtainable, the smaller pipe may be used. It is more than likely, though, that the reservoir is about 3000 feet or more away, and the entire fall available only about thirty feet or one foot in one hundred. Then an eight-inch pipe would have to be used.

Whether fire-protection piping, therefore, is a wise investment or not, depends largely on the cost of installation. A four-inch cast-iron pipe laid will cost about forty cents per running foot, while an inch pipe, large enough for everything except fires, will cost about ten cents, so that the excess cost per foot for the sake of fire protection is thirty cents, for a distance up to 500 feet (when the grade is 1 to 4) or $150. If the grade is not 1 to 4, then the pipe must be six-inch, and the excess cost is fifty cents or the cost for 500 feet will be $250. If the distance is greater than 500 and the fall not great, so that an eight-inch pipe has to be used, the excess cost is sixty-five cents a foot, or $650 for a 1000-foot line.

It is sometimes possible to economize by building a large tank containing about 36,000 gallons and using only a small pipe to fill, but always keeping the tank full. Such a tank would contain 4800 cubic feet or would be twenty-two feet square and ten feet deep, or it may be twenty-five feet in diameter and ten feet deep. This tank would have to be erected in the air, higher up than the top of the buildings, and would require heavy supports and a great expenditure. Unless, therefore, a convenient knoll or sidehill is available on which to build a concrete tank, the large pipe direct from the water-supply must be provided for fire protection. Whether it is worth while depends on the cost of insurance and whether it is considered cheaper to pay high rates for insurance or to spend the large sum for protection. A third choice is also open, namely, to carry no insurance and to install no fire hydrants and to run the inevitable risk of losing the house by fire. Perhaps the decision is a mark of the type of man whose property is concerned.

Rain water-supply.

It will often happen that no pond or brook is available for a water-supply, and if water is obtained, it must come directly from the rain. Apparently, this is quite feasible, since an ordinary house has about 1000 square feet area on which rain water might be caught and carried to a tank. In the eastern part of the United States, the annual rainfall is, on the average, 3-3/4 vertical inches per month, or the volume of water from the roof will be 310 cubic feet. This is nearly 80 gallons a day, or enough for three or four people. The rain from the house and barns might be combined, making perhaps 5000 square feet, and giving an ample volume of water for the needs of a dozen people.

In discussing the size of tank necessary to hold rain water for a family supply, it must be remembered that for many weeks at a time no rain occurs, and that a tank must be large enough to tide over these intervals of no rainfall. In the temperate zone there is no regularity in the monthly rates of rainfall. In the eastern part of the United States, the months of June and September are usually the months of least precipitation, although the general impression, perhaps, is that July and August have less rainfall than any other months. The truth is that, while wells and rivers are low in July and August, the actual rainfall for those months is not below the normal, and the low flows in the streams are caused by excessive evaporation and by the demands of growing crops. Although June and September have usually less rainfall than other months, in Boston the fall has been as high as 8.01 inches in June and 11.95 inches in September. Again, in Boston, typifying the eastern part of the United States, and taken because of the great length of rainfall statistics available there, the two months of highest rainfall on the average are March and August, and yet, in each month, in some particular year, the rainfall has been the lowest for any of the twelve months in the year.

As shown by statistics, the average rainfall in each month, taking a period of forty years or so, is practically constant for each month, and it is only the deviations from the average which would make trouble in a supply tank depending upon rainfall. Fortunately, statistics also show that while a month whose average rate of rainfall is three inches may be as low as three tenths of an inch, it is not often that two months of minimum rainfall come together, and in looking over the rainfall statistics the writer finds that for any three consecutive months, including the minimum, the amount of rainfall is generally two thirds of the monthly average for that year; and this is stated in this way because it gives what seems to the writer a basis for determining a fair and reasonable capacity of a rain-water storage tank. It depends, one will notice, on the average annual rainfall; that is, on the depth to which the rainfall would reach in any year if none ran off. This varies from about ten inches in the southeastern part of the United States to one hundred inches in the extreme northwest, the average for the eastern part of the country being about forty-five inches, so that the monthly average is 3.75 inches.