r 



WATER SUPPLY. 



WATER SUPPLY. 



784 



adopts, in calculating the diameter* to be given to Uia pipe*, the 



formula d = v - i in which g = the number of gallon* to be 



15 A 



delivered ; / = tlir length of the main in yard* ; A = the head in feet ; 

 and d, the diameter required, in inches. In Claudel's ' Formule* a 

 1'iuage de* Ingenieun,' there i* to be found a desvription of a more 

 elaborate and theoretically correct method of ascertaining the diameter* 

 of nib-main* ; but it U *o much more complicated than the one uied by 

 Mr. Hawkidey. that it will imliice for the purpose* of thi* Cyclopedia 

 to refer the reader to the work in which it i* explained. 



In carrying into effect a town diirtribution it i* necessary to observe 

 numerou* precaution*, in order to protect the pipe* from injury by 

 external causes. Thus, wherever gai- and water-pipe* are kid in 

 proximity to one another the water-pipe* ahould be laid at a lower 

 level than those conveying gM. In England it i* sufficient to place 

 the Kto-piprs at about two feet from the surface of the pavement; but 

 in order to protect the water-pipe* from the effect of frost, it i* neces- 

 sary to place them at least 4 feet below the same level : and in the 

 latitudes of Berlin, or of St. Petersburg, it has been found that 

 water-pipes have been frozen at even 6 feet from the surface of the 

 ground. In towns wherein the street traffic is exceptionally heavy the 

 vibrations of the ground may alao require that the pipes should bo 

 laid at a considerable depth, and indeed this detail may be considered 

 to vary in almost every case. It would ap)>ar that when the pipes 

 are laid at about 4 feet from the surface in our latitudes, the tempe- 

 rature of the water as it leaves the pipes will be sensibly the same, at 

 all seasons of the year, with its temperature at the moment of entry, 

 provided the motion be maintained in the pipes uniformly ; and it 

 tin nee follows that one of the best precautions which can be adopted 

 against frost is to maintain a constant circulation in the pipes. The 

 dilatation of the pipes from an increase of temperature must be taken 

 into account in laying down any system of town distrib tion ; and it 

 would appear from 11. Oirard's direct experiments that the average 

 rate of dilatation is equal to 0-00000300228 of a foot for every addi- 

 tional degree of Fahrenheit's scale, when the pipes ore free, and 

 in tl<e open air. In the ground M. Girard found that the temperatures 

 of the pipes were functions of the difference of temperatures of the 

 urn . unding media ; but that they were nearer to the temperature 

 of t e ground than to that of the water. The tendency of some 

 waters to produce deposits in the pipes they traverse must also be 

 taken into account, as it may ailect the discharge in a very serious 

 manner ; in some instances, in Yorkshire, the bores of the leading 

 mains have been known to have been thus diminished in a few years 

 to one half their sectional area by the deposition of the hydrous oxide 

 of iron ; in mains supplied directly from chalk or limestone springs 

 the same effect may be produced by the deposition of the bicarbonate 

 of lime. M. Payen states also that the slightly alkaline and aerated 

 waters are thoae which are the most likely to produce a dereiopmMri 

 of ttibercules of the hydrous oxide of iron in the interior of pipes 

 of that uietU : and that the oxidation takes place more rapidly upon 

 gray cast-iron than upon the whiter varieties. It ap|wars from experi- 

 ment, and from the results obtained in practice, that by coat 

 interior of water-pipes with a solution of hydraulic lime, or with lin- 

 seed oil containing litharge, the formation of the tuberciiles before 

 mentioned will be retarded; and in London the precaution of thus 

 coating the pipes is universally adopted. The chloride of sodium 

 when present in the water in small quantities, it may be added, 

 facilitate* the formation of the tubercules 



il within a few year* the distribution of water to the private 

 consumers was effected by the intermittent system, or by means of a 

 supply passed through the street-mains, at certain hours of the day, 

 into cisterns placed in the bouses, where it was stored for domestic 

 use as might be required- The cisterns, in such coses, are mule with 

 float-valves, such as the common ball-cock, Jiy '2 i valve 



fly. 3, which clone the delircry-uipe* when the water attains definite 



in tho first place, there i* so much oareleuncu in the matin, in hi. U 

 the cuterua are fixed and maintained in or.-, i . that the quality ol thu 

 water U very liable to be contaminated in private houses. The great 

 cisterns are, in fact, too ofton placed close to water closet* or sink* ; 

 the service-pipes to the water-closets often form a U.I-.-L commuuica- 



Flf . I. 





and, in addition to these means of stopping the supply when a 

 sullie.ent quantity of water has been <! <> citi us ore pro- 



Tilled with an o|n overflow pipe connected with the drainage of thu 



. thiough which the exces* of water may pass, if the machinery 

 for intercepting the flow should not not. It u found, however, that, 



tion between the pans of the closets and the water in the cisterns, so 

 that the gases from the one must escape through the 

 cisterns are loo often made of improp- Is; they are left 



exposed far too often to receive atmospheric impurities, dust, or soot; 

 and, incredible as it may sound, it is very rarely indeed that cisterns 

 are cleaned out from one year's end to another. The best water in thu 

 world so treated must be rendered more or less unfit for human con- 

 sumption; and it was principally ti . < -vil that t lie constant- 

 delivery system was introduced, avowedly because that system allowed 

 the cisterns to be dispensed with altogether. But it was also asserted 

 iiu constant-delivery system I 'my in the 

 supply of water, because it is found practically that in the 

 of dwellings the ball-cocks are either stolen or tieJ up. BO that the 

 excess of water was forcedly passed through the waste- or overflow- 

 pipe during a great portion of the time the street mains wire under- 

 charged. Unfortunately the economy has not been attained ; Ol 

 contrary, whenever the water supply of a town has remained in 

 ;h.- li nds of a municipality, it is found to be BO ditlicult to maintain 

 the necessary control and supervision over the distributor)' np]>aiatii, 

 that the waste upon the constant-delivery system has proved to be so 

 enormous that the system h.is practically been abandoned in many 

 cases. It really would appear that the only means by which the abuses 

 of the otherwise perfect method of delivery under constant pressure 

 could be prevented would be by enforcing the sale of water by n 

 and, indeed, as water is nearly as valuable as gas, there can be no 

 reason for selling the one by measure and not the other. Gas, in 

 London, costs i>. 6d. per 1000 cubic feet; water, at the rate of 6rf. per 

 1000 gallons, costs 3*. 1'3S</ per 1000 cubic feet. But hitherto no 

 water-meter bos been devised by means of which the water < 

 measured without intercepting the pressure ; so that at present there 

 appears to be an almost insuperable dilticulty in the way of the intro- 

 duction of the constant-delivery system in many towns about to con- 

 struct water-works de noro. In towns like London, the difli. 

 which would attend the modifications of the existing domestic arrange- 

 ments of tip- water -pipes would be so great, that it is to be feared the 

 present evils of the intermittent system will continue to be borne for 

 many years still to come. 



The water supplied to houses is, generally speaking, conducted from 

 the street-mains to the cisterns, and thence distributed where re. 

 by means of ! . on account of the ease with which th. 



be bent, so ns to accommodate themselves to the construction . 

 house. Some waters, however, especially those conta i \ ! ionic 



acid gat in suspension, act upon the lead with i "ergy and 



instance* of lead poisoning are by nu means uncommon when tho 

 waters distributed are remarkably soft. When waters exposed to this 

 danger must be used, it is necessary to employ cither wrou 

 tin, or composition service-pipes; but these Haters are far from being 



ven to these substitutes for the more flexible materi.il 

 The only other general remark* to be made with respect to house- 

 distribution of water are : 1, that thu apparatus for drawing the water 

 should be of such a nature as not to produce a hydraulic jar on its 

 being opened or closed ; '2, that the pipes should not be placed so as to 

 i the permeation of gases, or to the effects of heat or of 

 frost ; 3, that they should at all times be accessible for exam 

 repair. The thickness of service-pipes may be calculated upon the 



formula x =- 2111, in which x = the thickness sought, p - the pressure 



c r 



in Iba. per superficial in. li, r -- tho radius or half the internal diameter 

 of the pipo i i " strength of the mel 



. ial inch. Mi. II kncsscsofl 



i'ipes equal to 0'18 \Jd, or about J of tho stiuare root of the din- 

 u practice, lead-pipe* are made equal to ^t/ in small pipes, and to fal 

 in very large ones. 



The quantities of water required for the various details of domestic 

 distribution arc as follows ; 



