918
Object of house-drain.
House-drain to be self-cleansing.
Use of water for cleansing purposes.
No. 10.] THE ORDINANCES OF HONGKONG: [A.D. 1901
not in any elaboration of appliances, but in careful construction, careful and a reasonably liberal water supply. Without the co-operation of the public, the Sanitary Authority is almost powerless to effect improvement. It is therefore to be hoped that the public will assist, by insisting on good construction and the proper use of house-drains.
B. The object of a house-drain is to carry off, from the dwelling to the street-sewer, water fouled by use, together with all the solid or semi-solid refuse which is usually associated therewith, such as excrement of men and domestic animals, refuse from cooking, and the like; in short, the foul liquid usually known as sewage.
C. The house-drain must be "self-cleansing." The sewage as produced in the daily life of the inmates must flow through the drain with a current sufficiently rapid to sweep along with it all suspended matter, so that no permanent deposit can take place. A drain in which deposit takes place is a cesspool in disguise, from which offensive emanations find their way into the dwelling; and from which putrid sewage flows into the street-sewers, making them exceedingly offensive. A badly constructed or badly kept house-drain is, therefore, not only a source of danger to the inmates of the house that it drains, but a public nuisance also. Unless house-drains are well made and properly used, no system of street sewers, however perfect, can work in a satisfactory manner.
D. Water being the agent which cleanses the house-drains, its liberal use for cleansing by the inmates of the dwelling is essential to the proper maintenance of house-drains. The sewage must be well diluted. Nevertheless, the quantity of water necessary for the proper cleansing of house-drains is not excessive. The water normally used by the inmates of a dwelling for washing and cooking is sufficient for this purpose, provided that it is readily obtainable at all times, either in the dwelling or in close proximity thereto.
Principal point in design of house-drain.
Conditions of speed of stream in pipe.
E. The principal point to be attended to in the design of house-drains is so to arrange matters that the sewage, as produced, shall flow through them in the most rapid current practicable; so that all suspended matter shall be swept away at once and completely.
F.—(1.) The speed of a stream flowing through a pipe or channel, of given size and shape, depends upon the following conditions:—
(a.) the inclination of the channel;
(b.) the smoothness of its surface; and
(c.) the volume of the stream.
(2.) The steeper the slope and the smoother the sides of the channel, the swifter will be the current. The greater the volume of the stream, other things being the same, the greater the speed.
(3.) Thus if a 12" and a 3" pipe have the same inclination, the velocity in the 12" pipe would be about twice as great as in the 3" pipe, provided that both were half full. But to fill the two pipes to this extent, the quantity...
918
Object of house-drain.
House-drain to be self- cleansing.
Use of water
purposes.
No. 10.] THE ORDINANCES OF HONGKONG: [A.D. 19012 not in any elaboration of appliances, but in careful construction, careful and a reasonably liberal water supply. Without the co-operation of the publ the Sanitary Authority is almost powerless to effect improvement. It is ther fore to be hoped that the public will assist, by insisting on good construction and the proper use of house-drains.
B. The object of a house-drain is to carry off, from the dwelling to the street-sewer, water fouled by use, together with all the solid or semi solia refuse which is usually associated therewith, such as excrement of men on domestic animals, refuse from cooking, and the like; in short, the foul liquid usually known as sewage.
C. The house-drain must be "self-cleansing." The sewage as produced in the daily life of the inmates must flow through the drain with a current sufficiently rapid to sweep along with it all suspended matter, so that no permanent deposit can take place. A drain in which deposit takes place in cesspool in disguise, from which offensive emanations find their way into the dwelling; and from which putrid sewage flows into the street-sewers, makin them exceedingly offensive. A badly constructed or badly kept house-drain is, therefore, not only a source of danger to the inmates of the house that it drains, but a public nuisance also. Unless house-drains are well made and properly used, no system of street sewers, however perfect, can work in satisfactory manner.
D. Water being the agent which cleanses the house-drains, its liberal use for cleansing by the inmates of the dwelling is essential to the proper maintenance of house-drains. The sewage must be well diluted. Nevertheless, the quantity of water necessary for the proper cleansing of house-drains is not excessive The water normally used by the inmates of a dwelling for washing and cooking is sufficient for this purpose, provided that it is readily obtainable ab all times, either in the dwelling or in close proximity thereto.
Principal point in design of house-drain.
Conditions of speed of
stream in pipe.
E. The principal point to be attended to in the design of house-drains in so to arrange matters that the sewage, as produced, shall flow through them in the most rapid current practicable; so that all suspended matter shall be swept away at once and completely.
F.-(1.) The speed of a stream flowing through a pipe or channel, of given size and shape, depends upon the following conditions :—
(a.) the inclination of the channel;
(b.) the smoothness of its surface; and
(c.) the volume of the stream.
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(2.) The steeper the slope and the smoother the sides of the channel swifter will be the current. The greater the volume of the stream, being the same, the greater the speed.
(3.) Thus if a 12" and a 3" pipe have the same inclination, the velocity in the 12" pipe would be about twice as great as in the 3" pipe, provided that both were half full. But to fill the two pipes to this extent, the quantity
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