998 [ 24 of 1887. ) PUBLIC HEALTH .
Bye-laws made by the Sanitary Board of Hongkong, under s. 13, sub - s. 1 ,
and approved by Legislative Council 13th October, 1890.
( Gazette 18th of same month .)
Preliminary Explanatory Notes.
A. The following notes convey, in general terms, the principles that should
guide the design and construction of house - Irains. Before proceeding to lay
down in detail the instructions which should be attended to, in order to apply
the same satisfactorily ; it must be observed that no code of instructions can
possibly embrace every case that will occur . It must be remembered that no
system of house - drainage that has yet been devised, or probably will ever be
devised, does away with the necessity for care in use . The real remedy for
the inconveniences which are too often experienced from house-drains lies,
not in any elaboration of appliances, but in careful construction, careful use,
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, hy 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 excrementof men or
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 rapidl 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 -ulrain 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
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 -ulrains, 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.
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. The speed of a stream flowing throngh a pipe or channel, of given size
and shape, depends upon the following conditions:
(a.) The inclination of the channel.
(6.) The smoothness of its surface.
(c. ) The volume of the stream .
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 , inclination being
the same, the greater the speed .