CHAPTER XIV.

=141. Introductory.=—A preceding lecture in this course has shown to what an advanced state the public supply of water to large cities was developed in ancient times. The old Romans, Greeks, Egyptians, and other ancient peoples evidently possessed an adequate appreciation of the value of efficient systems of public water-supply. Very curiously that appreciation diminished so greatly as almost to disappear during the middle ages. The demoralization of public spirit and the decrease of national power which followed the fall of Rome induced, in their turn, among other things, a neglect of the works of the great water system of Rome, entailing their partial destruction. The same retrogression in civilization seemed to affect other ancient nations as well, until probably the lowest state of the use of public waters and the construction of public water systems was reached somewhere between A.D. 1000 and A.D. 1300 or 1400. Without reasonable doubt the terrible epidemics or plagues of the middle ages can be charged to the absence of suitable water-supplies and affiliated consequences. During that middle period of the absence of scientific knowledge and any apparent desire to acquire it, sanitary works and consequently sanitary conditions of life were absolutely neglected. No progress whatever was made toward reaching those conditions so imperative in large centres of population for the well-being of the community. Grossly polluted waters were constantly used for public and private supplies, and no efforts whatever were made among the masses toward the suitable disposition of refuse matters or, in a word, to attain to sanitary conditions of living.

A few important works were completed, particularly in Spain, but nothing indicative of general relief from the depths of ignorance and sanitary demoralization to which the greater portion of the civilized world had sunk at that time. The city of Paris took all its water from the Seine, except that which was supplied by a small aqueduct built in 1183. So small was the supply, aside from the water obtained from the river, that in 1550 it is estimated that the former amounted to about one quart only per head of population per day. The situation in London was equally bad, for it was only in the first half of the thirteenth century that spring-water was brought to the city by means of lead pipes and masonry conduits. Public water-works began to be constructed in Germany on a small scale in the early part of the fifteenth century. Obviously no pumps were available in those early days of water-supply, so that the small systems which have been mentioned were of the gravity class; that is, the water flowed naturally in open or closed channels from its sources to the points of consumption. Pumps of a simple and crude type first began to be used at a point on the old London Bridge in 1582, and in Hanover in 1527. Subsequently to those dates other pumps were set up on London Bridge, and installations of the same class of machinery were made in Paris in 1608, usually operated by water-power in some simple manner, as by the force of the water-currents. In 1624 the Paris supply received a reinforcement of 200,000 gallons per day by the completion of the aqueduct Arcueil. The New River Company was incorporated in 1619 for the partial supply of the city of London, and it began to lay its pipes at that time. As its name indicates, it took its supply from New River, and the inception of its business is believed to mark the first application of the principle of supplying each house with water. This company is still in existence and furnishes a considerable portion of the present London supply.

=142. First Steam-pumps.=—The application of steam to the creation or development of power by Watt, near the end of the eighteenth century, stimulated greatly the construction of water-works, as it offered a very convenient and economical system of pumping. It seems probable that the first steam-pumps were used in London in 1761. Twenty years later a steam-pump was erected in Paris, while another was installed in 1783. The second steam-pump in London was probably constructed in 1787. In all these earlier instances of the use of steam-pumps river supplies were naturally used.

=143. Water-supply of Paris and London.=—After the early employment of steam pumping-machinery demonstrated its great efficiency for public water-supplies, the extension of the latter became more rapid, and since 1800 the supplies of the two great cities of London and Paris have been greatly increased. As late as 1890 the Paris supply amounted to about 65 gallons per head of population, one fourth of which was used as potable, being drawn from springs, while three fourths, drawn from rivers, was used for street-cleaning or other public purposes. This supply, however, was found inadequate and was re-enforced in 1892 by an addition of 30,000,000 gallons per day of potable water brought to the city by an aqueduct 63 miles long. Another addition of about 15,000,000 gallons has been provided more recently.

Rather curiously the water-supply of London is afforded by eight private companies, one of which is the old New River Company already mentioned. These companies, with one exception, draw their supply mainly from the rivers Thames and Lea, all such water being filtered. The remaining company draws its water from deep wells driven into the chalk. The total population supplied amounts to about 5,500,000, the rate of supply being thus less than 45 gallons per head per day.

=144. Early Water-pipes.=—Inasmuch as the use of cast-iron for pipes was only begun about the year 1800, other materials were used prior to that date. As is well known, the pipes used in ancient water-works were either of lead or earthenware. In the eighteenth century wooden pipes made of logs with their centres bored out were used, sometimes 6 or 7 inches in diameter. As many lines of these log pipes were used as needed to conduct a single line of supply. In the earlier portion of the nineteenth century such log pipes, usually of pine or spruce, were used by the old Manhattan Company for the supply of New York City. A section of such a wooden pipe, with a bore of about 2½ inches is preserved in the museum of the Department of Civil-Engineering of Columbia University. Large quantities of such pipes were formerly used.

=145. Earliest Water-supplies in the United States.=—The earliest system of public water-supply in this country was completed for the city of Boston in 1652. This was a gravity system. It is believed that the first pumping-machinery for such a supply was set up for the town of Bethlehem, Pa., and put in operation in 1754. Subsequently water-supplies were completed for Providence, R. I., 1772, and for Morristown, N. J., in 1791; the latter has maintained a continuous existence since that date. The first use of steam pumping-machinery in this country was in Philadelphia in 1800. This machinery, curiously enough, was largely of wood, including some portions of the boiler; it was necessarily very crude and would perform with 100 pounds of coal only about one twenty-fifth or one thirtieth of what may be expected from first-class pumping-machinery at the present time. Other cities and towns soon began to follow the lead of these earlier municipalities in the construction of public water-supplies, but the principal development in this class of public works has taken place since about 1850.

It is estimated that the total population supplied in 1880 was about 12,000,000, which rose to about 23,000,000 in 1890, and it is probably not less than 50,000,000 at the present time.

=146. Quality and Uses of Public Water-supply.=—Advances in the public supplies in this country have been made rather in the line of quantity than quality. Insufficient attention has been given both to the quality of the original supply and to the character of the reservoirs in which it is gathered until within possibly the past decade. A few cities like Boston have scrutinized with care both the quality of the water and the character of the bottom and banks of reservoirs, and have spared neither means nor expense to acquire a high degree of excellence in their potable water. The same observations can be applied to a few other large cities, but to a few only. The realization of the dependence of public health upon the character of water-supply, however, has been rapidly extending, and it will doubtless be but a short time before the care exercised in collecting and preparing water for public use will be as great in this country as in Europe, where few large cities omit the filtration of public waters.

The distribution of water supplied for public use is not limited to domestic purposes, although that class of consumption controls public health so far as it is affected by the consumption of water. The applications of water to such public purposes as street-cleaning and the extinguishing of fires are of the greatest importance and must receive most careful consideration. Again, the so-called system of water-carriage in the disposal of domestic and manufacturing wastes, constituting the field of sewage-disposal, depends wholly upon the efficiency of the water-supply.

=147. Amount of Public Water-supply.=—The first question confronting an engineer in the design of public water-supply is the amount which should be provided, usually stated on the basis of an estimated quantity per head of population. This is not in all cases completely rational, but it is by far the best basis available. If the water-supply is designed for a small city or town previously supplied by wells or other individual sources, the first year’s consumption will be low per head of population for the reason that many people will retain their own sources instead of taking a share of the public supply. As time elapses that portion of population decreases quite rapidly in numbers, and in a comparatively few years practically the whole population will use the public supply. In communities, therefore, where public systems have long existed and it is desired either to add to the old supply or to install new ones, the only safe basis of estimate is the entire population.

=148. Increase of Daily Consumption and the Division of that Consumption.=—The amount of water required per head of population might naturally be assumed identical with the past consumption, but that would frequently be incorrect. It is one of the most prominent features of the history of public water-supplies in this country that the consumption per head of population has increased with great rapidity from the early years of the installation of the different systems, for reasons both legitimate and illegitimate. The daily average consumption of water from the Cochituate Works of the Boston supply increased from 42 gallons per head of population in 1850 to 107 gallons in 1893, and in the Mystic Works of the same supply the increase was from 27 gallons in 1865 to 89 gallons in 1894. Again, the daily average consumption in Chicago rose from 43 gallons per head per day in 1860 to 147 gallons in 1893, while in Philadelphia during the same period the increase was from 36 gallons per head per day to 150 gallons. In Cambridge, Mass., the increase in daily average consumption per head of population was from 44 gallons in 1870 to 70 gallons in 1894. These instances are sufficient to show that, under existing conditions, the daily consumption was increased at a rapid rate in the cities named, and they have been selected as fairly representative of the whole field. Civil engineers have made extended studies in connection with this question in a great number of cities, for it bears upon one of the most important lines of public works. It is absolutely essential to the health and business prosperity of every city that the water-supply should be abundant, safe, and adapted to the industrial and commercial pursuits of its population. It is imperative, therefore, that the division of the daily supply should be carefully analyzed. For this purpose the water-supply of a city may be, and frequently is, divided into four parts:

(1) That used for domestic purposes; (2) That used for commercial and industrial purposes; (3) That used for public purposes; (4) That part of the supply which is wasted.

1. That portion of the supply consumed for domestic purposes includes not only the water used in private residences, but in those branches of consumption which may be considered of a household character found in hotels, clubs, stores, markets, laundries, and stables, or for any other residential service. As might be expected, this branch of consumption varies largely from one city to another. The results of one of the most interesting and suggestive studies ever made in connection with this subject are given by Mr. Dexter Brackett, M. Am. Soc. C. E., in the Transactions of the American Society of Civil Engineers for 1895. In Boston the purely domestic consumption varied in different houses and apartments from 59 gallons per head per day in costly apartments down to 16.6 gallons per head per day in the poorest class of apartment. In Brookline, one of the finest suburbs of Boston, the quantity was 44.3 gallons per day. In some other cities of Massachusetts, as Newton, Fall River, and Worcester, this class of consumption varied from 6.6 gallons to 26.5 gallons per day, the latter quantity being found at Newton in some of the best residences, and the former at houses also in Newton having but one faucet each. In Yonkers, N. Y., where the system was metered, the amount was 21.4 gallons per head of population per day, while in portions of London, England, it varied from 18.6 to 25.5 gallons per head per day. The average of these figures gives a result of 18.2 gallons per head per day, which, in round numbers, may be put at 20 gallons.

2. It is obvious that the rate of consumption for commercial and industrial purposes in any city must vary far more than that for domestic purposes, for the reason that some cities may be essentially residential in character while others may be essentially manufacturing. At the same time, it is to be remembered that many manufacturing establishments may have their own water-supply. The city of Fall River, Mass., is eminently a manufacturing city, yet Mr. Brackett found that the manufacturing demand on the public water-supply amounted to 2 gallons only per inhabitant per day, as the manufacturers draw the most of their supply from the river, but that where the manufacturers depend upon the public supply for all their water the amount rises to a value between 20 and 30 gallons per inhabitant. In Boston in 1892 the water consumed for all manufacturing and industrial purposes, including railroads, gas-works, elevators, breweries, etc., amounted to 9.24 gallons per head of population per day, while in Yonkers in 1897 the total consumption for commercial purposes was 27.4 gallons per head per day. In the city of New York, as nearly as can be estimated, the consumption for commercial purposes is probably not far from 25 gallons per inhabitant per day. Reviewing all these results, it may be stated that the water consumption for commercial and industrial purposes will generally range from 10 to 30 gallons per inhabitant per day.

3. The consumption of water for public purposes is a smaller amount than either of the two preceding. It covers such uses as public buildings, schools, street-sprinkling, sewer-flushing, fountains, fires, and other miscellaneous objects, more or less similar to those just named. The total use of this character was 3.75 gallons per inhabitant per day for Boston in 1892, and 5.57 gallons per inhabitant per day for Fall River in 1899. A few other cities give the following results: Minneapolis in 1897, 5 gallons; Indianapolis, 3 gallons; Rochester, N. Y., 3 gallons; Newton, Mass., 4 gallons; Madison, Wis., 10 gallons. In Paris it is estimated that not far from 2.5 gallons per head of population per day are used. It is probable, therefore, that an amount of 5 gallons per day per inhabitant will cover this particular line of consumption.

4. A substantial portion of the water-supply of every city fails to serve any useful purpose, for the reason that it runs to waste either by intention or by neglect. The sources of this waste are defective plumbing, including leaky faucets and cocks; deliberate omission to close faucets and cocks, constituting wilful waste; defective or broken mains, including leaky joints; and waste to prevent freezing.

=149. Waste of Public Water.=—All these wastes except the last are inexcusable. There is no difficulty in detecting defective plumbing, and its existence is generally known to the householder; but if the wasted water is not measured and paid for, it is far too frequently considered more economical to continue the waste than to pay for the plumber’s services. In a multitude of cases cocks are left open indefinitely for all sorts of insignificant reasons; in closets, under the erroneous impression that the continuous running of the stream will materially aid in a more effective cleansing of soil- and sewer-pipes, failing completely to appreciate that a far more powerful stream is required for that purpose; sometimes in sinks, for refrigerating purposes, and in many other inexcusably wrong ways. These sources of wilful waste lead to large losses and constitute one of the most unsatisfactory phases of administration of a public water system. Such losses result in a vicious waste of public money. The amount of water flowing from leaky joints and from leaks in pipes and mains is necessarily indeterminate because it escapes without evidence at the surface except in rare cases. In every instance where examinations have been made and a careful record kept of the amount of water supplied to a city, it has been found that the aggregate of the measured amounts consumed fail nearly to equal the total supply. There are probable errors both in the measurement of the quantities supplied and in the quantities consumed, but the large discrepancy cannot be accounted for in this manner. In many cases consumed water has even been carefully measured by meters, as at Yonkers, New York, Newton, Milton, and Fall River, Mass., Madison, Wis., and at other places, but yet the discrepancy appears to be nearly as wide as ever. Again, in 1893 observations were carefully made on the consumption of the water received by the Mystic supply of the Boston system at _all_ hours of the twenty-four. Obviously between 1 and 4 A.M. the useful consumption should be nearly nothing, but, on the contrary, it was found to be nearly 60 per cent of the average hourly consumption for the entire twenty-four hours. The waste at Buffalo, N. Y., in 1894 was estimated at 70 per cent of the total supply. Similar observations in other places have given practically the same results. It has also been found that, in a number of instances, where old watercourses have been completely obliterated by considerable depths of filling required by the adopted grades of city streets and lots, and excavations for buildings have subsequently been opened practically the full volume of the former streams are flowing along the original but filled channel. This result has been observed under a practically impervious paved city surface. It is difficult to imagine the source of such a supply except from defective pipe systems or sewers. A flow of a least 100,000 gallons per day from a broken pipe which found its way into a sewer has also been discovered without surface evidence. These and many other results of experience conclusively demonstrate that much water flows to waste unobserved from leaky joints and defective or broken pipes.

Inasmuch as cast-iron water-pipes are produced in lengths which net 12 feet as laid, there will be at least 440 joints per mile. Furthermore, as leaky joints and broken pipes are as likely to occur at one place as another, it seems reasonable to estimate leakage through them as proportionate to the length of the pipe-line in a system; and that conventional law is frequently assumed. New pipe-lines have sometimes shown a leakage of 500 to 1200 gallons per mile of line per day. Civil engineers have sometimes specified the maximum permissible leakage of a new pipe-line at 60 to 80 gallons per mile of line per day for each inch in diameter of pipe, thus permitting 600 to 800 gallons to escape from a 10-inch pipe. In 1888 the late Mr. Chas. B. Brush reported a leakage of about 6400 gallons per mile per day from a practically new 24-inch cast-iron main, 11 miles long, of the Hackensack Water Company, the pressure being 110 pounds per square inch. Tests of water-pipes in German and Dutch cities have been reported as showing less waste than 300 gallons per mile per day, but such low results, unless for very low pressures and short lines, may reasonably be doubted. Obviously losses of this character will probably increase with the age of the pipe. By a very ingenious procedure based upon his own experience, Mr. Emil Kuichling of Rochester, N. Y., reaches the conclusion that a reasonable allowance for the waste from leaky joints and defective pipes is 2500 to 3000 gallons per mile of cast-iron pipe-line per day. If, as is frequently the case, the population per mile of pipe ranges from 300 to 1000, the preceding allowance amounts to 3 to 10 gallons per head of population per day. The loss or waste due to running cocks or faucets to prevent freezing cannot be estimated with sufficient accuracy to receive a definite valuation, but it must be considered an element of the total item of waste.

=150. Analysis of Reasonable Daily Supply per Head of Population.=—It has repeatedly been found that the losses or wastes set forth in the preceding statements amount apparently to quantities varying from 30 to 50 per cent of the total supply; or, to put it a little differently, the water unaccounted for in even the best systems now constructed apparently may reach one third to one half of the total supply. This is an exceedingly wasteful and unbusinesslike showing. It is probable that the statement is, to some extent at least, an exaggeration. It is practically certain that either the amount supplied or the amounts consumed, or both, are never measured with the greatest accuracy, and that the errors are such as generally swell the apparent quantity wasted. After making judicious use of the data thus afforded by experience, it is probable that the following tabular statement given by Messrs. Turneaure and Russell represents limits within which should be found the daily average supply of water in a well-constructed and well-administered system.

+---------------------------+--------------------------------+ | | Gallons per Head per Day. | | Use. +----------+----------+----------+ | | Minimum. | Average. | Maximum. | +---------------------------+----------+----------+----------+ | Domestic | 15 | 25 | 40 | | Industrial and commercial | 5 | 20 | 35 | | Public | 3 | 5 | 10 | | Waste | 15 | 25 | 30 | +---------------------------+----------+----------+----------+ | Total | 38 | 75 | 115 | +---------------------------+----------+----------+----------+

The values given in the preceding table are reasonable and sufficient to supply the legitimate needs of any community, but, as will be shown in the succeeding table, there are cities in this country whose average consumption is more than twice the maximum rate given above.

=151. Actual Daily Consumption in Cities of the United States.=—The following table exhibits the average daily consumption of water throughout the entire year for the cities given, as determined for the years indicated in the table.

The city of Buffalo shows a daily consumption of 271 gallons per inhabitant, and Allegheny, Pa., 247 gallons per inhabitant. There are a considerable number showing an average daily consumption per inhabitant of 160 gallons or more. All such high averages exhibit extravagant use of water, or otherwise inefficient administration of the water-supply. The reduction of such high rates of consumption is one of the most difficult problems confronting the administration of public works. The use of the meter has proved most efficient in preventing wastes or other extravagant consumption, as in that case every consumer pays a prescribed rate for the amount which he takes.

TABLE I.

-------------------+-----------+----------+-------+----------- | | | |Consumption | | | Per | per |Population.|Population|Cent of| Inhabitant | | per Tap. | Taps | Daily, | | |Metered| Gallons. -------------------+-----------+----------+-------+----------- | 1890. | 1890. | 1890. | 1890. -------------------+-----------+----------+-------+----------- New York | 1,515,301 | 13.9 | 20.2 | 79 Chicago | 1,099,850 | 7.1 | 2.5 | 140 Philadelphia | 1,046,964 | 6.1 | 0.3 | 132 Brooklyn | 838,547 | 8.7 | 2.5 | 72 St. Louis | 451,770 | 11.8 | 8.2 | 72 Boston | 448,477 | 6.6 | 5.0 | 80 Cincinnati | 305,891 | 8.5 | 4.1 | 112 San Francisco | 298,997 | 9.9 | 41.4 | 61 Cleveland | 270,055 | 8.7 | 5.8 | 103 Buffalo | 255,664 | 6.3 | 0.2 | 186 New Orleans | 242,039 | 54.0 | 0.4 | 37 Washington | 230,392 | 6.5 | 0.3 | 158 Montreal | 216,000 | 5.3 | 1.7 | 67 Detroit | 205,876 | 5.1 | 2.1 | 161 Milwaukee | 204,468 | 11.1 | 31.9 | 110 Toronto | 181,000 | 4.0 | 4.1 | 100 Minneapolis | 164,738 | 16.5 | 6.3 | 75 Louisville | 161,129 | 11.9 | 5.9 | 74 Rochester | 133,896 | 5.4 | 11.4 | 66 St. Paul | 133,156 | 12.7 | 4.2 | 60 Providence | 132,146 | 9.4 | 62.4 | 48 Indianapolis | 105,436 | 35.6 | 7.6 | 71 Allegheny | 105,287 | 7.0 | 0 | 238 Columbus | 88,150 | 11.5 | 6.4 | 78 Worcester | 84,655 | 8.9 | 89.4 | 59 Toledo | 81,434 | 18.6 | 9.4 | 72 Lowell | 77,696 | 9.2 | 22.9 | 66 Nashville | 76,168 | 14.9 | 0.8 | 146 Fall River | 74,398 | 14.9 | 74.6 | 29 Atlanta | 65,533 | 20.0 | 89.6 | 36 Memphis | 64,495 | 11.9 | 3.7 | 124 Quebec | 63,000 | 10.4 | 0 | 160 Dayton, O. | 61,220 | 20.0 | 3.8 | 47 Camden, N. J. | 58,313 | . . . | . . . | 131 Des Moines, Ia. | 50,093 | 20.0 | 60.0 | 55 Ottawa, Ont. | 44,000 | 4.2 | 0 | 130 Yonkers, N. Y. | 32,033 | 12.0 | 82.4 | 68 Newton, Mass. | 24,379 | 5.5 | 67.4 | 40 Madison, Wis. | 13,426 | 11.0 | 31.0 | 40 Albany, N. Y. | 98,000 | . . . | 0.4 | 162 New Bedford, Mass. | 55,000 | . . . | . . . | 99 Springfield, Mass. | 49,299 | . . . | . . . | 87 Holyoke, Mass. | 40,000 | . . . | . . . | 77 -------------------+-----------+----------+-------+----------- -------------------+-------+-----------+----------- | |Consumption|Consumption | Per | per | per |Cent of| Inhabitant| Inhabitant | Taps | Daily, | Daily, |Metered| Gallons. |Gallons. -------------------+-------+-----------+----------- | 1895. | 1895. | 1900. -------------------+-------+-----------+----------- New York | 27.0 | 100 | 115 Chicago | 2.8 | 139 | 190 Philadelphia | 0.74 | 162 | 229 Brooklyn | 1.9 | 89 | . . . St. Louis | 7.4 | 98 | 111 Boston | 5.2 | 100 | 143 Cincinnati | 6.5 | 35 | 121 San Francisco | 28.0 | 63 | 73 Cleveland | 4.5 | 142 | 175 Buffalo | 0.85 | 271 | 262 New Orleans | . . . | 35 | 48 Washington | 1.5 | 200 | 174 Montreal | 1.6 | 83 | . . . Detroit | 8.2 | 152 | 156 Milwaukee | 51.0 | 101 | 84 Toronto | 3.7 | 100 | Minneapolis | 16.0 | 88 | 93 Louisville | 6.6 | 97 | . . . Rochester | 18.0 | 71 | 83 St. Paul | 1.7 | 60 | 51 Providence | 74.0 | 57 | 54 Indianapolis | 7.1 | 74 | 79 Allegheny | 7.1 | 247 | . . . Columbus | 9.3 | 127 | 183 Worcester | 90.0 | 66 | 67 Toledo | 35.0 | 70 | 59 Lowell | 33.0 | 82 | 83 Nashville | 24.0 | 139 | 140 Fall River | 82.0 | 35 | 35 Atlanta | 99.0 | 42 | 61 Memphis | 4.6 | 100 | 98 Quebec | 0 | 170 | . . . Dayton, O. | 24.0 | 50 | 62 Camden, N. J. | 0 | 200 | 185 Des Moines, Ia. | 42.6 | 43 | 48 Ottawa, Ont. | 0 | 0 | . . . Yonkers, N. Y. | 99.8 | 100 | 76 Newton, Mass. | 77.3 | 65 | 62 Madison, Wis. | 61.0 | 52 | 44 Albany, N. Y. | 12.3 | . . . | 192 New Bedford, Mass. | 15.4 | . . . | 101 Springfield, Mass. | 31.9 | . . . | 88 Holyoke, Mass. | 5.82 | . . . | [4]103 -------------------+-------+-----------+------------

[4] Estimated.

=152. Actual Daily Consumption in Foreign Cities.=—It has been for a long time a well recognized fact that the daily use of water in American municipalities is far greater per inhabitant than in European cities. It is difficult to explain the marked difference, but it is probably due in large part to the more extravagant general habits of the American people. Examinations in a number of cases have shown that the actual domestic use of water, at least in some of the American cities, is not very different from that found in corresponding foreign cities. Table II exhibits the consumption of water in European cities, as compiled from various sources and given by Turneaure and Russell.

TABLE II.

---------------------------------------+-------------+----------- | |Consumption | Estimated | per Capita City. | Population. | Daily, | | Gallons. ---------------------------------------+-------------+----------- England, 1896-97:[5] | | London | 5,700,000 | 42 Manchester | 849,093 | 40 Liverpool | 790,000 | 34 Birmingham | 680,140 | 28 Bradford | 436,260 | 31 Leeds | 420,000 | 43 Sheffield | 415,000 | 21 Nottingham | 272,781 | 24 Brighton | 165,000 | 43 Plymouth | 98,575 | 59 Germany, 1890 (Lueger): | | Berlin | 1,427,200 | 18 Breslau | 330,000 | 20 Cologne | 281,700 | 34 Dresden | 276,500 | 21 Düsseldorf | 144,600 | 25 Stuttgart | 139,800 | 26 Dortmund | 89,700 | 78 Wiesbaden | 62,000 | 20 France, 1892 (Bechmann): | | Paris | 2,500,000 | 53 Marseilles | 406,919 | 202 Lyons | 401,930 | 31 Bordeaux | 252,654 | 58 Toulouse | 148,220 | 26 Nantes | 125,000 | 13 Rouen | 107,000 | 32 Brest | 70,778 | 3 Grenoble | 60,855 | 264 Other countries, 1892-96 (Bechmann): | | Naples | 481,500 | 53 Rome | 437,419 | 264 Florence | 192,000 | 21 Venice | 130,000 | 11 Zurich | 80,000 | 60 Geneva | 70,000 | 61 Amsterdam | 515,000 | 20 Rotterdam | 240,000 | 53 Brussels | 489,500 | 20 Vienna | 1,365,000 | 20 St. Petersburg | 960,000 | 40 Bombay | 810,000 | 61 Sidney | 423,600 | 38 Buenos Ayres | 680,000 | 34 ---------------------------------------+-------------+-----------

[5] Compiled, except the figures for London, by Hazen. _Engineering News_, 1899, XLI. p. 111.

These foreign averages, with three exceptions, represent reasonable quantities of water used, and they have been confirmed as reasonable by many special investigations made in this country.

=153. Variations in Rate of Daily Consumption.=—The preceding observations are all based upon an average total consumption found by dividing the total annual consumption by the number of days in the year. This is obviously sufficient in a determination of the total supply needed, but it is not sufficient in those matters which involve a rate of supply during the different hours of the day, or the amount of the supply for the summer months as compared with those of the winter. As a general rule the greatest supply will be required during the hot summer months when lawn- and street-sprinkling is most active. It appears from observations made in a considerable number of the large cities of the United States that the maximum monthly average consumption may run from about 110 to nearly 140 per cent of the monthly average throughout the year. As an approximate value only, it may be assumed for ordinary purposes that the maximum monthly demand will be 125 per cent of the average.

The daily rate taken throughout the year is considerably more variable than the monthly. There are days in some portions of the year when consumption by hotels and industrial activities is at a minimum. On the other hand, there are other days when those activities are at a maximum and the total draft will be correspondingly high. Experience has shown that the maximum total draft may vary from about 115 to nearly 200 per cent of the average. It is permissible, therefore, to take approximately for general purposes the maximum total daily consumption as 150 per cent of the average. Manifestly any total consumption will have an hourly rate which may vary greatly from the early morning hours, when the draft should be almost nothing, to the forenoon hours on certain days of the week, when the draft is a maximum. These variations have frequently been investigated, and it has been shown that the maximum rate per hour of a maximum day may sometimes rise higher than 300 per cent of the average hourly rate for the year. These considerations obviously attain their greatest importance in connection with the capacity of the plant, either power or gravity, from which the city directly draws its supply. The hourly capacity of the pumps or steam-plant furnishing the supply need not necessarily be equal to the maximum, since storage-reservoirs may be and usually are used; but the capacity of the pipe system leading from such storage-reservoirs must be equal to the maximum hourly rate required.

=154. Supply of Fire-streams.=—The draft on a water-supply for fire-extinguishing purposes may have an important influence upon the hourly rate of consumption. These observations are particularly pertinent in connection with the water-supply of small cities where the draft of fire-engines may be considered a large percentage of the total hourly consumption. It is obviously impossible to assign precisely the number of fire-streams which may be required simultaneously in a city having a given population, but experiences of a considerable number of civil engineers furnish reasonable bases on which such estimates may be made. Table III exhibits such estimates as made by the civil engineers indicated. It is given by Mr. Emil Kuichling in the Transactions of the American Society of Civil Engineers for December, 1897. Probably no more reasonable estimate can be now presented.

TABLE III.

TABLE EXHIBITING ESTIMATED NUMBER OF FIRE-STREAMS REQUIRED SIMULTANEOUSLY IN AMERICAN CITIES OF VARIOUS MAGNITUDES.

---------------+------------------------------------------------- | Number of Fire-streams Required Simultaneously. Population of +-----------+-----------+-----------+------------- Community. | 1 | 2 | 3 | 4 | Freeman. | Shedd. | Fanning. | Kuichling. ---------------+-----------+-----------+-----------+------------- 1,000 | 2 to 3 | .. | .. | 3 4,000 | .. | .. | 7 | 6 5,000 | 4 to 8 | 5 | .. | 6 10,000 | 6 to 12 | 7 | 10 | 9 20,000 | 8 to 15 | 10 | .. | 12 40,000 | 12 to 18 | 14 | .. | 18 50,000 | .. | .. | 14 | 20 60,000 | 15 to 22 | 17 | .. | 22 100,000 | 20 to 30 | 22 | 18 | 23 150,000 | .. | .. | 25 | 34 180,000 | .. | 30 | .. | 38 200,000 | 30 to 50 | .. | .. | 40 250,000 | .. | .. | .. | 44 300,000 | .. | .. | .. | 48 ---------------+-----------+-----------+-----------+-------------

The discharge of each fire-stream will of course vary with its diameter and the pressure at the fire-engine, but as an average it is reasonable to assume that each stream will discharge 250 gallons per minute. The quantity of water required, therefore, to supply the estimated number of streams given in Table III is found by simply multiplying the number of those streams by 250, to ascertain the total number of gallons consumed per minute. If _x_ is the number of thousand inhabitants in any city, and if _y_ represents the required number of streams, then Mr. Kuichling deduces the following formulæ for _y_ by the use of the preceding tables, i.e., these formulæ express the results given in the preceding table as nearly as simple forms of formulæ permit. ___ { _y_ min. = 1.7√_x_ + 0.033_x_,} { } For Freeman’s data: { _x_ } (1) { _y_ max. = --- + 10. } { 5 } ____ ___ For Shedd’s data: _y_ = √5_x_ = 2.24 √_x_. (2)

_x_ For Fanning’s data: _y_ = --- + 9. (3) 10 ___ For the author’s data: _y_ = 2.8 √_x_. (4)

While for the average ordinary consumption of water, expressed in gallons per head and day, _q_, Mr. Coffin’s formula, as given in his paper previously cited, may be taken

_q_ = 40_x_⁰˙¹⁴. (5)

By combining equation (5) with equation (4), remembering that the maximum rate of consumption is usually about 1.5 times the average, the total draft in gallons per minute upon the discharging system at the time of a conflagration will become as follows:

___ 3 40 × 1000 _Q_ = 250(2.8 √_x_) + ---- ---------- _x_¹˙¹⁴ 2 1440

( ___ _x_¹˙¹⁴) = 250(2.8√_x_ + --------) (6) ( 6 )

This maximum rate of consumption during a conflagration does not affect the total supply of a large city like New York, Boston, or Chicago, but it may become of relatively great importance in a small city or town. In a large city this draft may and frequently does tax the capacity of a small district of the discharging system. In designing such systems, therefore, even for large cities, it is necessary to insure all districts against a small local supply when a large one may pressingly be needed.