_SOURCES OF WATER-SUPPLY_
Having arrived at the quantity of water necessary to supply the needs of
the average household, we must next investigate the possible sources
from which this quantity 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 space 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.
[Illustration: FIG. 24.--Diagram of a spring.]
[Illustration: FIG. 25.--Water finding its way from a hillside.]
[Illustration: 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 quantity, 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 asserted 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 quantities 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 quantity, 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 shores 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
coarseness of the material affected the quantity of water that had to be
pumped from the trenches,--the finest sand requiring only one hand pump
at a time, while the coarse 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 coarse 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 quantity 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, Massachusetts, 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.
[Illustration: 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.
[Illustration: 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 pass 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.
[Illustration: 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.
[Illustration: 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 quantity 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.
[Illustration: 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 quantity 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 quantity 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 space 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 Canal, in connection with
the Barge Canal Work, and in New York City, in connection with building
foundations.
[Illustration: FIG. 32.--Sinking a well by means of a water-jet.]
Sometimes, when a shallow dug well does not furnish the required
quantity 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 quantity furnished and partly because of
difficulty in acquiring title 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.
[Illustration: 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._
[Illustration: 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.
More simply it may be made by digging a trench along the hillside at the
same level as the spring, or into the spring if necessary to find the
water, and then laying draintile surrounded by coarse gravel or broken
stone in the trench.
In the western part of the country much knowledge has been gained by
investigating and experimenting on this kind of spring water
development, only there the springs have been made artificially by
digging down to meet the underground flow of water. For example, in the
Arkansas River Valley, California, where it was suspected that water was
flowing underground, a trench was dug transversely across the valley,
and at a depth of six feet sufficient water was found to amount to
200,000 gallons per day for each one hundred feet of trench. On the
South Platte River, near Denver, much the same thing has been done, and
in a trench eighteen feet deep, water is collected at the rate of a
million and a quarter gallons per day for each one hundred feet of
trench. Other examples of the same sort might be given.
For a single house, the spring need usually only be extended by means of
a short trench, and three-inch terra-cotta tile should be laid in the
trench and surrounded by gravel and then covered over. The spring
receiving water from these tiles should be inclosed, as will be
described in a later chapter.
_Supply from brooks._
Whenever a spring is not available and at the same time a supply of
running water by gravity is determined on for a house, recourse is
generally had to brooks which may find their way down the hillsides in
the vicinity. In many instances the water in such brooks is practically
spring water and is the overflow of actual springs. Where the brook is
not subject to contamination between the spring and the point at which
the supply is taken, the latter is as truly spring water as the former,
and if a long length of pipe is saved, there can be no objection to the
brook supply. On the other hand, it is suggestive, at least, of
misrepresentation for a summer hotel or boarding house to advertise that
their water-supply comes from springs when really it comes from an open
brook miles away from the spring which may be indeed the origin of the
brook, but with so many intervening opportunities for contamination that
the pure original source is unrecognizable.
There are two obvious drawbacks to the use of brooks: (1) that the
quality of the water is, in many cases, objectionable, and (2) that
brooks are very apt to dry up in summer on account of their limited
watersheds. The discussion on the first point will be postponed to a
later chapter, and we have now to consider the question of quantity
only.
The wisest plan before deciding on a brook supply is to measure the
volume of water which flows in the brook at the time when it is lowest,
probably about the middle of August. The actual volume of water needed
for the household is not large, although its required rate of flow may
be high and, as already pointed out, a stream which furnishes water at
the rate of one quart in five minutes is sufficient for a family of
three persons, a rate which is almost a drop-by-drop supply. Such a
stream would require a reservoir somewhere in order to supply the
faucets at the proper rate, and for a single family a small cistern or
even a barrel sunk in the ground would be sufficient for this purpose.
An objection to the utilization of so small a flow in connection with
the smaller storage is that the temperature of the water in summer is so
raised that vegetation and animal growths take place easily and freely,
so that the taste and smell of such water is most disagreeable. These
consequences can be avoided even with the low flow by increasing the
storage, since the larger quantity of water has been found to resist the
bad effects of the low flow and high temperature. Figure 35 shows a
small reservoir actually in use to supply water for a single house.
[Illustration: FIG. 35.--A reservoir for home use.]
_Storage reservoirs._
But even if the stream actually dries up for two or three months, it is
still possible to use it for water-supply, provided a suitable location
for a dam and pond can be found where storage, as described in the
preceding chapter, can be secured. For this reason as well as for the
greater benefit to the quality of the water, brooks flowing through
rough, wooded, and uninhabited country are to be preferred as a source
of water-supply to brooks flowing through flat agricultural land, and in
many cases, where their flow is largely due to springs, the brooks
themselves may compare favorably with springs in quality.
_Ponds or lakes._
Water may be properly taken from ponds or lakes whenever the danger from
pollution is negligible. No better source of supply can be imagined than
a pond in the midst of woods, far away from human habitation, presumably
furnishing an unlimited supply of pure soft water. Sometimes water from
such ponds contains large amounts of vegetable matter, the result of
decomposition of swampy or peaty material, as, for instance, from the
ponds in the Dismal Swamp of Virginia, so that the water has a yellow,
coffee-colored appearance. The appearance of such water is suspicious,
but it need not be feared unless something more pernicious than the
coloring matter is present.
As the country becomes more settled, ponds are more and more likely to
become contaminated and hence unfit for a water-supply, and this
possibility must be taken into account in planning for a water-supply.
It would be most shortsighted to carry a long line of pipe from a house
to a pond several miles away, only to have the pond made unfit for use
within a few years by the growth of the community around the pond. The
possibility of cooeperation ought not to be overlooked, however. It is
quite possible that half a dozen householders might be so located with
respect to each other and to a pond that an arrangement could be made
whereby the owner of a small pond would agree to fence it around and
dedicate it to the purposes of a water-supply, doing this as his share.
The others might then well afford to pipe the water to one house after
another, including that of the owner of the pond.
Water from a pond or lake has one great advantage over water from a
brook, namely, that contaminating substances in the pond settle out, so
that pond water, especially if the pond is deep, is always of much
better quality than running water. For this same reason, water taken
from a reservoir on a stream is much better water than that in the
stream above the reservoir indicates, and pollution is much less to be
feared where the reservoir exists.
_Pressure for water-supplies._
The value of a high pressure in the water-pipes of a house has been much
overestimated. For a number of years the water-supply in the writer's
residence came from a tank in the attic, the pressure in the bath-room
being not more than ten feet, and while the water flowing through a
three fourths inch pipe was noticeably slow, it was not so slow as to
discredit the supply.
A height or head of twenty feet above the highest fixture in the house
would be better and ought to be secured whenever possible. This head is
obtained by having the source of supply higher than the highest fixture,
not merely the twenty feet mentioned, but also an additional height
necessary to offset the frictional losses caused by the running water.
The loss from this source in case of fire supply has already been
referred to, but for purely domestic supplies the loss is appreciable.
The maximum rate as already indicated is not more than 7000 gallons per
day, whereas the fire rate both for single houses and for a small hamlet
is about a million gallons a day. For the lower rate, as well as for
rates one half and twice this rate, the friction loss in vertical feet
per 100 feet run in small pipes is shown in the following table:--
TABLE X. SHOWING LOSS OF HEAD BY FRICTION, FOR DIFFERENT QUANTITIES OF
FLOW, AND IN DIFFERENT SIZES OF PIPES
========================================================================
Rate of Flow | | | | |
in Gallons | | | | |
Per Day | 1/2" Pipe | 5/8" Pipe | 3/4" Pipe | 1" Pipe | 1-1/4" Pipe
-------------+-----------+-----------+-----------+---------+-------------
3500 | 13.95 | 4.81 | 2.35 | 0.66 | 0.25
7000 | 47.17 | 17.30 | 7.45 | 2.04 | 0.74
14000 | 163.09 | 57.8 | 25.00 | 6.64 | 2.41
========================================================================
The table shows how much additional elevation is needed over the 20 feet
already referred to. For example, suppose it is decided that a rate of 1
quart in 10 seconds is to be maintained from three faucets or a rate of
7000 gallons per day. Suppose that a pond 4000 feet away is found to be
50 feet above the highest faucet in the house, and it is a question what
size pipe ought to be used. By the table a 1-inch pipe loses 2.6 feet
per 100 feet or 104 feet in the 4000 feet, an impossible amount when
only 50 feet are available, although the size would be entirely proper
if the difference of level was 124 feet or anything greater. A
1-1/4-inch pipe, however, loses only 0.74 foot in 100 or 39 feet per
mile, so that the 1-1/4-inch pipe would be necessary, although that size
would answer even if the pond were a mile and a quarter away.
When water from a well is pumped to an elevated tank there is the same
necessity of providing about 20 feet difference in level between the
tank and the highest fixture, but the length of pipe involved being
small, the friction losses are not great. It should be noted even here
that too small a pipe may reduce the pressure, a 1/2-inch pipe causing a
loss of 47 feet in a 100-foot pipe line. If a tower is built by the side
of the house, the distance down to the ground, across to the house, and
up to the second floor would hardly be less than 50 feet, and this is a
loss of 23-1/2 feet, which means that the tank would have to be set
higher in the air by this amount. With a 3/4-inch pipe, it should go 3.7
feet, and with a 1-inch pipe but a foot higher than the level necessary
to make the water flow out of the faucet at the rate already specified.