ORDINANCE No. 24 OF 1887. 2209
Public Health.
prevent the accumulation of sewage-tainted air therein, and to secure the efficiency of
the traps. To effect this thoroughly, the drain must have, at or near its extremities,
openings giving a free escape to the air within it, and between these openings, there
should be no trap or other obstruction to the free passage of air.
O. These ventilating-openings should be so placed that any sewage-tainted air
which may escape from them shall be as little offensive as possible. With this object
the inner ventilating-opening should be placed above the roof of the dwelling. This is
usually done by carrying up a pipe, having a free opening at the top, above the roof ;
and at a distance from any window. The second opening is usually made on the house
side of the trap which severs the direct communication between the drain and the
public sewer. If, however, there be no trap between the house-drain and the sewer
then there is no necessity for a second opening, the sewer itself serving the purpose.
With a well constructed system of self- cleansing street- sewers this arrangement may
be adopted with safety, even with advantage. Then every house-drain ventilator
serves as a sewer ventilator also ; and when this is done universally, no accumulation of
sewer-tainted air can take place in any part of the system.
P. Care must be taken in selecting the position of the lower ventilating opening,
because the elevated ventilating pipe by no means secures a permanent upward current
of air. According to the relative temperature of the air within and without the drain ,
to the direction and force of the wind , so an upward or downward current will obtain.
Q. Complete ventilation is especially important when any part of the house-drain
system is in communication with the interior of the dwelling ; or where the system is
extensive and has numerous inlets . It is essential where water- closets are used, or
where the drains receive excrementitious matter. In the case of a short length of
drain, leading from a single inlet, placed in an open space, such as a back-yard, though
desirable, it is less necessary and may be omitted without serious danger.
R. Any direct communication between the interior of the house and the house
drain shoul be avoided . Pipes carrying water from baths or sinks, within the dwelling,
should therefore deliver their effluent above trapped gulleys , in the open air. The
effluent from baths or sinks, on upper storeys should , whenever practicable, be received
by open- topped pipes, delivering freely above trapped gulleys at or a little below the
ground-level . If, as in the case of water-closets, a direct communication has to be
made between a fitting inside the house and the drain, then there must be complete
ventilation by means of a pipe carried up outside and to the top of the building .
BYE-LAWS .
1. Any owner or occupier of private premises about to construct any new drain, Notices.
shall give at least seven days' previous written notice of such intention to the Board,
and such notice shall be delivered at the office of the Board, in a form of which
printed blank copies may be obtained gratis in English and Chinese on application at