Rural Hygiene Part 7

If the well is a driven well and the water in the casing falls so low that the ordinary suction pump will no longer draw, two remedies may be applied. A so-called deep-well pump may be used; that is, a pump which fits inside the piping and can be lowered down to the water level. The ability to bring up water then depends on the power to work the pump and on the presence of the water. Figure 22 shows the principle on which this pump works. At some point, it may be three or four hundred feet below the surface of the ground, a valve _A_ opening upward is set in the well so that it is always submerged. Just above this is a second valve fastened to the lower end of the long pump rod which reaches up to the engine or windmill which operates the pump. At each up stroke water is lifted by the closed valve _B_ and sucked through the open valve _A_.

At each down stroke, the water is held by the closed valve _A_ and forced up through the open valve _B_.

[Ill.u.s.tration: FIG. 23.--Pump installation.]

The other method of developing a greater quant.i.ty of water from a deep well is to use air pressure to force the water either the entire distance to the tank or to a point where the suction of an ordinary pump can reach it, as indicated in Fig. 23. In this method an air blower is needed, and since this means an engine for operation, it is not generally feasible, but is suited to occasional needs, where an engine is already installed for other purposes and is therefore available.

The operation is very simple. An air pipe leads from a blower and delivers compressed air at the end of the air pipe, which must be below the level of the water in the well. The pressure of the air then causes the water to rise, the distance depending on the pressure at which the air is delivered.

CHAPTER VI

_SOURCES OF WATER-SUPPLY_

Having arrived at the quant.i.ty of water necessary to supply the needs of the average household, we must next investigate the possible sources from which this quant.i.ty can be obtained. Before the advantages of running water in the house are understood, a well is the normal and usual method of securing water, although in a few cases progressive farmers have made use of spring water from the hillsides. It is rare, indeed, for surface water, so called, to be used for purposes of water-supply until after modern plumbing conveniences have been installed. Then the use of surface water becomes almost a necessity because of the large volume of water needed. The only drawback to its use is its questionable quality. Without modern plumbing, a well meets the requirements of family life, but does not answer the demands of convenience. With modern plumbing, a well is found to be pumped dry long before the domestic demands are satisfied. The result is an attempt to secure an unfailing supply, and for this a surface supply is sought.

Let us divide, then, the possible sources of water for domestic consumption into two groups, those found under the surface of the soil and those found on or above the surface. In the first group will come wells and springs, and in the second group will come brooks, streams, and lakes.

_Underground waters._

Springs result from a bursting out of underground waters from the confined s.p.a.ce in which they have been stored or through which they have been running. Thus in Fig. 24 is seen how water falling on the pervious area _a-b_ is received into the soil and gradually finds its way downward between impervious strata which may be clay or dense rock. At the point _B_, where the cover layer has, for any reason, been weakened, the pressure of the water forces its way upward and a spring is developed at the point _C_. Or, conditions may be as shown in Fig. 25, where the confined water, instead of being forced upward by pressure, flows slowly out from the side of a hill, making a spring at the point _D_, while the water enters the pervious stratum at the point _a-b_ as before.

[Ill.u.s.tration: FIG. 24.--Diagram of a spring.]

[Ill.u.s.tration: FIG. 25.--Water finding its way from a hillside.]

[Ill.u.s.tration: FIG. 26.--The sinking of wells.]

If the water is held in the ground as in the first case, it is possible to develop the spring artificially; that is, to drill through or bore through the overlying impervious strata so as to allow the escape of the water. When this happens, the water bursts forth exactly as in a natural spring except that under some conditions the pressure may be sufficient to force the water rising in a pipe instead of through the ground to flow above the surface of the ground as a fountain or jet, making what is known as an "artesian well." A true well, on the other hand, may be put down in the ground and through strata where springs could never develop; that is, where no pressure exists in such a way as to bring the water to the surface, as in Fig. 26. The well here is sunk until it reaches the water, and it is safe to say that one can always reach a layer of water in the ground by a well if the well is deep enough.

The flow of underground water is, however, always very uncertain and confusing, and even in localities where water would naturally be expected in quant.i.ty, as, for instance, in the bottom of a valley filled with glacial drift, much disappointment is often experienced because the expected water is not found. The city supply of Ithaca, New York, is a case in point. For six miles south of the lake there is a broad, almost level valley filled many hundred feet deep with glacial drift and presumably filled with water flowing at some unknown depth below the surface into the lake. When the city was recovering from the typhoid fever epidemic which, in 1903, committed such ravages, well water seemed to the panic-stricken citizens the only safe water. Geologists were called in, and they gravely a.s.serted that the valley contained glacial drift to a great depth and that an ample supply of pure water could be counted on. It was known that water was met all through this valley at depths of from six to twelve feet and then that there would be found a layer of finely powdered silt to a depth of about one hundred feet, when another layer of water would be found, and that all the private wells reached this layer. When tested by the city, however, it was found that this water-bearing stratum was of too fine material to yield its water freely, and the supply from the depth was altogether inadequate. In one section of the town large quant.i.ties of good water were found at a depth of about three hundred feet, and the city thought that other wells of the same depth should add to the quant.i.ty, but experiment showed that this three hundred-foot water was limited to one particular section, and after a considerable expenditure of money, an underground water-supply for the city was given up.

_Ordinary dug well._

The ordinary well at a farmhouse is what is known as a shallow well or sometimes a "dug well," usually ten to twenty feet deep. This type does not usually pierce any impervious layer and thus reach a water-bearing stratum, otherwise inaccessible. The water is found almost at the surface, and the depth of the well is only that necessary to reach the first water layer. A very good example of this kind of well is to be found on the south sh.o.r.es of Long Island Sound, where a pipe can be driven into the sand at any point, and at a depth of a few feet an abundant and cheap supply of water may be secured. The amount of water that such a well can furnish depends upon the area from which the water comes and upon the size of the particles of sand or gravel through which the water has to percolate, it being evident that the finer the material, the more difficult for the water to penetrate.

The writer remembers superintending the digging of trenches in the streets of a city where the texture of the soil varied continually from clay to sand and even to gravel, all saturated with subsoil water into which wells could have been dug. It was very striking to see how the coa.r.s.eness of the material affected the quant.i.ty of water that had to be pumped from the trenches,--the finest sand requiring only one hand pump at a time, while the coa.r.s.e gravel required either a dozen men or a steam pump to keep a short trench reasonably free from water. The same conditions exist when a well is in operation, modified by the fact that the coa.r.s.e material yielding a larger supply will be most quickly exhausted unless the area drained is very large.

A shallow well is most uncertain as to its quant.i.ty and is likely to be of doubtful quality. There are, however, some examples of shallow well supplies which furnish large amounts of water; as, for instance, the one at Waltham, Ma.s.sachusetts, or at Bath, New York,--the latter, a dug well some twenty feet in diameter and about twenty-eight feet deep, furnishing a constant supply of good water to a village of about 4000 people.

_Construction of dug wells._

The construction of shallow wells requires little comment. Ordinarily, they are dug down to the water, or to such a depth below the level of the water as is convenient, by the use of an ordinary boat pump to keep down the water, and then are stoned up with a dry wall. Such a well for a single house requires an excavation of about eight feet diameter, with an inside dimension of about five feet.

[Ill.u.s.tration: FIG. 27.--Mode of sinking a well.]

If the soil at the bottom of the well is sandy, it is possible to take a barrel or a large sewer pipe and sink it into the bottom of the well in the water by taking out material from the inside and loading the outside to keep it pressed down into the sand. This same plan may be used to sink the whole body of the well wall, first supporting the lower course of masonry on a curb, so called (see Fig. 27). This curb is usually made of several thicknesses of two-inch plank well nailed together, the plank breaking joints in the three or four layers used. It is a good plan to have this shoe or curb extend outwardly beyond the walls of the well so that some clearance may be had, otherwise the dirt may press against the walls so hard as to hold it up and prevent its sinking. While this arrangement may be put down in water, it requires some sort of bucket which will dig automatically under water and has not been therefore a customary method except for large excavations where machinery can be installed. There is no reason, however, why the method might not be used for a single house.

[Ill.u.s.tration: FIG. 28.--A well that will catch surface waste.]

In whatever way the well is dug, one point in the construction that needs to be emphasized is that the wall should be well cemented together, beginning about six feet below the surface and reaching up to a point at least one foot above the surface. This is to prevent pollution from the surface gaining direct access to the well, and if this cementing is well done for the distance named, it is not likely that any surface pollution in the vicinity of the well could ever damage the water. Figure 28 shows the section of a well where no such precautions have been taken, and it is evident that not only surface wash, but subsurface pollution may readily contaminate the water. Figure 29 (after Imbeaux), on the other hand, shows a shallow well properly protected by a good wall and water-tight cover. Figure 30 shows a photograph also of this latter type of well. Even if a cesspool or privy is located dangerously near the well, in the second case the fact that the contaminating influence must pa.s.s downward through at least six feet of soil before it can enter the well is a guarantee that the danger is reduced to the smallest possible terms.

[Ill.u.s.tration: FIG. 29.--A well properly protected.]

_Deep wells._

Deep wells are of the same general character as shallow wells. Usually, the ground on which the rainfall occurs is more distant, so that the source of the water is often unknown, and usually, also, the stratum from which the water comes is overlaid by an impervious one.

[Ill.u.s.tration: FIG. 30.--A properly protected well.]

It often happens that there are several layers of water or of water-bearing strata alternating with more or less impervious strata, and that wells might be so dug as to take water from any one of them.

Indeed, not infrequently in driving down a pipe to reach water, a fairly satisfactory quant.i.ty is obtained at a certain level, and then, in order to increase the supply, the pipe is driven further, shutting off the first supply and reaching some other, less abundant.

Deep wells are reached usually by wrought-iron pipe driven into the ground. Sometimes this is done by taking a one-and-one-quarter inch pipe, with its lower end closed and pointed, and driving it with wooden mauls into the ground. When it has gone six or eight feet, it is pulled up, cleared from the earth, and replaced, to be driven six feet again.

[Ill.u.s.tration: FIG. 31.--Well-drilling apparatus.]

With ordinary soil, the pipe is easily withdrawn with a chain wrench, and two men will drive one hundred feet in a couple of days. When water is reached, a well point is put on through which water may percolate without carrying too much soil. This type of well is suitable for use in soft ground or sand, up to depths of about one hundred feet, and in places where the water is not abundant. It is most useful for testing the ground to see where water may be found and by pumping from such a well to see what quant.i.ty of water may be expected. This type is often used as a shallow well, and the author has seen such wells driven only a dozen feet. Such a well has no protection against pollution, and an ordinary dug well is better for shallow depths. A driven well always has a disadvantage also from the ever present danger that the iron pipe will rust through at the top of the ground water and so admit to the well the most polluted part of the drainage.

For larger supplies and for greater depths, a machine like a pile-driver has to be used for forcing down the pipe. This is not usually removed, but driven down as far as possible, and when the limit of the machine has been reached, a smaller size is slipped down inside the driven pipe, to be in turn driven to refusal. In rock, that is, if the well has to penetrate a layer of rock, a drill is used that will work inside of the pipe last driven, and by alternately lifting and dropping the drill, and at the same time twisting it back and forth, a hole through rock may be made many hundred feet below the surface of the ground. Figure 31 shows a cut of a common type of well-drilling machine.

In some soils, not rock, it is necessary to keep the drill going in order to churn up or soften the earth so that the pipe may be lowered.

The churned-up soil is removed by a sand pump, which is a hollow tube with a flap valve at the lower end opening inwards and a hook on the upper end. By alternately drilling, pipe-driving, and pumping the wet material, length after length of pipe can be forced into the ground until water of a satisfactory quant.i.ty is reached. Very often a jet of water is used to wash out the dirt from the interior of the well instead of a sand pump. As shown by Fig. 32 water under pressure is forced down the small pipe _A_ which runs to the bottom of the well. The large pipe _B_ can then, as the sand is loosened by the water, be driven down by the one thousand-pound hammer _M_. The water and sand together flow up in the s.p.a.ce outside the small pipe and inside the large pipe, overflowing through the waste pipe _W_. This type of well has been very largely used throughout New York State; on Long Island, in connection with the Brooklyn Water-supply; along the Erie Ca.n.a.l, in connection with the Barge Ca.n.a.l Work, and in New York City, in connection with building foundations.

[Ill.u.s.tration: FIG. 32.--Sinking a well by means of a water-jet.]

Sometimes, when a shallow dug well does not furnish the required quant.i.ty of water, the amount of water can be increased by driving pipe wells down into water strata below the one from which the dug well takes its supply, so that water will rise to the strata penetrated by the dug well. This has been done to increase the public supplies at Addison and Homer in New York State. Unfortunately, much uncertainty exists in the matter of the yield of driven wells, and an individual undertakes a deep well usually with great reluctance on account of the expense involved and the uncertainty of successful results. In level ground, conditions are not likely to vary in the same valley, so that if one well is proved successful, the probabilities are that wells in the vicinity will be equally so, and yet, at some places, the contrary has proved to be true.

One may estimate the cost of putting down four-inch driven wells as approximately one dollar per foot besides the cost of the pipe, which will be about fifty cents per foot. The cost of one-and-one-half-inch pipe would be considerably less than fifty cents, the cost of driving varying not so much with the size of the pipe as with the soil conditions. The writer recently paid ninety dollars for driving two one-and-one-half-inch wells to a depth of about one hundred feet, the above cost including that of the pipe; the soil conditions, however, were very favorable. In Ithaca the cost of driving one-and-one-quarter-inch pipe is fifteen cents per lineal foot up to about fifty feet deep with the cost of the pipe fifteen cents per foot additional. Below fifty feet deep the cost increases, since the labor and time required for pulling up the pipe is largely increased, and at the same time the rate at which the pipe will drive is notably diminished.

The question of pumping from wells will be considered in a later chapter, together with methods of construction and operation.

_Springs._

Springs should be the most natural method of securing water-supply for a detached house, since no expense is involved except that of piping the water to the building. In Europe, spring water-supplies have been greatly developed in furnishing water for large cities. Vienna, for example, with its population of nearly two millions, obtains its water-supply from springs in the Alps mountains, and many smaller cities do likewise.

But in this country springs have been little used for water-supplies, partly because of the uncertain quant.i.ty furnished and partly because of difficulty in acquiring t.i.tle to the water rights. If an individual, however, has on his farm, or within reach, a spring furnishing a continuous supply of water, it would seem quite absurd not to make use of such a Heaven-sent blessing. Care must be taken always that a spring is not contaminated by surface drainage, and for this reason, as with shallow wells, the wall surrounding the inclosed spring should be extended above the ground and made impervious to water for at least six feet below the surface. In some cases it may be wise to convert an open spring into an underground one, putting a roof over all and then covering with earth and sod. Figure 33 shows a type suggested by the French engineer, M. Imbeaux.

[Ill.u.s.tration: FIG. 33.--An inclosed spring.]

Very often a larger supply from a spring may be obtained by collecting into one basin a number of separate and smaller springs. A swampy or boggy piece of ground is often the result of the existence of a number of springs, and if drains are laid to some convenient corner of the field, and a well dug there, into which the drains will discharge, not only will the swamp be drained, but an ample supply of water in this way be obtained. It would, of course, not be wise to have cows pasture in this part of the field, nor, even when the ground has been dried out, should this field be manured or cultivated. It should rather be fenced and left to grow up in underbrush, dedicated to the farm water-supply.

_Extensions of springs._

[Ill.u.s.tration: FIG. 34.--A spring extension.]

Again, if the water comes from a stratum W-W, as shown in Fig. 34, a large additional yield can be obtained by extending the spring from the point where it breaks out along the edge of the water-bearing stratum on each side. This extension or gathering conduit can be made by building rough stone walls on each side of the ditch, covering with flat stones so as to form a pervious channel to intercept the water and lead it to the chamber from which the supply pipe to the house leads out. The ground-water level will then be altered as shown by the broken line in the draining.