Mechanics of the Household / A Course of Study Devoted to Domestic Machinery and Household Mechanical Appliances

by E. S. Keene

CONSTRUCTION OF WELLS

Wells are constructed by different methods, depending on the character of the soil in which they are sunk. Their excavation is usually accomplished by one of three general methods: by digging; by driving a pipe into the earth until it penetrates the water-bearing stratum; or by boring a hole with an enlarged earth auger, into the water-bearing soil. Artesian wells are made by drilling with a device suitable for making a small and very deep hole.

Dug Wells.

—In shallow wells the water seeps through the soil from local precipitation. Deep wells are those from which the water is brought to the surface through an impervious geologic formation, as a bed of clay or rock, and from a depth greater than that from which water may be lifted by atmospheric pressure. The fact that a deep well originates from a source that entirely differs from that of the shallow well accounts for the difference in chemical composition which frequently exists in the water from the two types of wells in the same neighborhood.

The form of the dug well is generally that of a cylindrical shaft 4 feet or more in diameter and of depth depending on the location of the water-bearing stratum. Where the character of the soil is such that the seepage is slow and the water does not flow into the well as fast as the pump will remove it, the well must contain a considerable volume to supply the period of greatest demand. Wells of this kind are commonly walled with brick or stone to keep the sides in place and to prevent the entrance of surface waters. The top of this curb should be brought above the surface of the ground and should be made water-tight to prevent the entrance of surface waters. The space around the curb, at the surface, should be graded to drain the water away from the well. There should be no chance for the water to collect in pools about the well; it should be conducted away in a gutter to the place of final disposal. The well should be covered with a platform of concrete or planking which will allow no water to enter from the surface.

Wells of this order are sometimes dug to great depth before the water-bearing stratum is encountered; this may sometimes be reached only after a great amount of expense and labor. The historic Joseph Well, near Cairo, Egypt, is an open shaft, 18 by 24 feet in area, sunk through solid rock 160 feet.

Open Wells.

—Open wells have long been condemned as insanitary. The familiar open well of the “Old Oaken Bucket” type is an inviting receptacle for the deposit of all manner of refuse, which once inside remains until it is disintegrated. These wells become the final resting place of many small animals and all manner of creeping things, in search of water. The open top receives wind-blown matter in the form of leaves and dust, much of which is in the nature of polluting material.

Fig. 125.—Ideal form of well curbing with cover and drain made of concrete.

The Ideal Well.

—In the case of a well which yields pure water, every precaution should be taken to prevent its pollution. The ideal form of construction is that shown in Fig. 125. In this well, the curbing C is of heavy concrete that extends above the natural surface of the ground, to prevent the entrance of surface water, and that from seepage through the upper stratum of the soil. The reinforced-concrete top forms a close joint with the curb to prevent the entrance of waste water and all animal life. The pump is of iron, secured to the well cover by bolts, set in the concrete. The trough of concrete G conducts the waste water from the well to a safe distance. The earth about the well is so graded as to permit no water to stand in pools.

Coverings of Concrete.

—The use of concrete for the coverings of wells, cisterns and springs has become a recognized form of the best construction. It is not more expensive than other good materials and when properly executed it forms an imperishable protection and gives a neat appearance. The spring cover in Fig. 126, and the cistern top in Fig. 127 are illustrations of its application.

Artesian Wells.

—Artesian wells are made by boring into the earth until the drill reaches the artesian stratum, the internal pressure forces the water through the opening to the surface. They are usually small in diameter and often of great depth. In some areas the artesian flow is found a few feet below the surface, but generally it is much deeper and 3000 feet is not an unusual depth.

The pressure and amount of flow from these wells is sometimes sufficient to permit the water being used for the generation of power. Small waterwheels are not uncommonly driven in this way and the power used for the generation of electricity for lighting and running small household appliances.

Driven Wells.

—In localities where the nature of the soil gives opportunity, wells are made by driving a pipe to the required depth. Wells of this character are usually made in places where the water-bearing soil is of sand or gravel. The pipe terminates in a sand-point such as that of Fig. 128. This sand-point is a perforated pipe with a pointed end, that facilitates driving. The perforations, as shown in the point P, form a strainer which allows the water to enter the pipe but prevents the sand from filling the opening.

Fig. 126.—Concrete cover for a spring.

Fig. 127.—Concrete cistern top.

In the use of driven wells, the water-bearing soil must be sufficiently open to allow the water to flow into the pipe as fast as the pump takes it away.

Bored Wells.

—In many localities the water-bearing stratum is of such nature as to give a ready flow of water but yet not sufficient to permit of the use of a sand-strainer; if, however, the opening is somewhat enlarged, the water will enter with sufficient rapidity to supply a pump. In such cases bored wells are quite generally used. They are made by boring a hole of the required size with an earth auger. These wells are made of any size up to 2 feet in diameter. They are often called tubular wells because they are lined with iron tubing or tile, to prevent the earth from refilling the hole.

Fig. 128.—Driven well with a sand-point strainer.

Cleaning of Wells.

—Very few dug wells are so constructed as to exclude dust and washings from the ground. It is, therefore, necessary that they be occasionally cleaned. Accumulations from these causes may be sufficient to hinder the entrance of the water to the well and thus lessen its capacity.

Gases in Wells.

—One of the commonest gases found in wells is carbon dioxide (carbonic acid gas). It may be detected by lowering a lighted candle or lantern to the bottom. If the gas is present in dangerous quantity, the flame will be extinguished. Death from asphyxiation due to this gas is not an uncommon occurrence, to persons descending into wells. Before entering a well, the test described above should be applied, as a precaution against accident. Carbon dioxide is a colorless, odorless gas in which a person will drown as readily as in water.

Peculiarities of Wells.

—Owing to the formation of the water-bearing earths, from which they receive their water, many wells possess marked peculiarities of behavior that often give rise to local reputation because of their vagaries. These characteristics have been classified into breathing wells, blowing wells, sucking wells, etc. These effects are in almost every case due to variation of barometric pressure. The ordinary level of the water in a well is governed by the variation of rainfall, melting of snow or the release of water by the thawing of frozen ground. It often occurs, however, that the head of water is markedly influenced by storms, when a rise of the level of the water occurs at the time of low barometric pressure during the storm period. This effect is often noticed in flowing wells. Many wells, at the approach of storms, yield roily water to such an extent that where the water is normally clear it may become for a period entirely unfit to drink, because of the matter held in suspension. All of these effects are accounted for by the varying atmospheric pressure. At the time of high barometer, a well that ordinarily flows freely will have to be pumped, the additional pressure of the air holding back the water to an extent representing several feet of head. The change of an inch in the barometric pressure will produce slightly more than a foot in head of water. At the time of storms, the barometer is sometimes abnormally low which will produce a corresponding rise of water in the well. At such time the free flow of water into a dug well, from the usual source of supply, will cause such a rapid flow of water through the passages in the earth as to carry with the water the sediment that produces roily water in the well. This sediment will settle after a while and the water will again be clear.

Breathing Well.

—Wells of this kind are most common in areas where the water-bearing earth is of rock formation; particularly in limestone areas, where caves and cavities are common. It sometimes happens that in the neighborhood of a well there is a cavity in the earth of considerable volume, the only entrance to which is through the well and that being under usual conditions covered by water, a foot or more in depth. With such a formation the conditions are right for a breathing well. At times of high barometer the water is depressed and the air will flow into the cavity through the well, when the well is said to inhale. This inward flow of air will continue until the air pressure in the cavity is equal to that of the outer air; and if the cavity is large and the opening small, the inward flow of air may continue for hours, even for days. With a fall of barometric pressure, the air in the cavity, being at a higher pressure than the external air, the air will flow outward and the well is said to exhale.

Freezing Wells.

—In cold climates, particularly in territory possessing cavernous limestone deposits, breathing wells often freeze in winter. When large volumes of frigid air are drawn into a well, the amount of heat taken from the water is sufficient to freeze it, and stop the supply of water. This effect is sometimes remedied by plugging the well at the top, so that the influx of cold air is prevented and the water does not freeze.