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sewer gas—at least, at times, and under certain conditions.
In old, badly-laid, ill-kept, defective, unflushed and ill-ventilated
sewers—what are known as sewers of deposit, or elongated
underground cesspools—these deleterious and dangerous
gases are generated in excess, and may prove a
danger to health by causing nausea, vomiting, diarrhoea,
sore throats, headache, and general malaise and lowering of
the vitality, thereby predisposing to various diseases (zymotic
and others). The need for ventilation (thorough and efficient)
is, therefore, obvious, and, as far as our knowledge and experience
at present goes, such ventilation may be best effected by
the provision of (a) open ventilating grids at the road levels
(such grids being in sufficient numbers) in the middle of
fairly wide thoroughfares; and (b) properly constructed
shafts of proper dimensions and calibre, for it is needless to
state that a shaft of 4 ins. by 3 ins. will not compensate for
an open grid 12 ins. by sins. In this way, the sewer gases
are diluted and oxidised, and thereby rendered innocuous
and inert.
Old sewers being, more or less, filled with such deleterious
and dangerous gases, it is self-evident that all house
drains should be disconnected, as far as possible, from such
sewers by the provision of suitable, efficient, and properly
constructed intercepting traps (and man-holes or other
equally efficient means of access); otherwise these deleterious
and dangerous gases would pass into, or near, the
rooms (living and sleeping) of houses through any defect
that might be present in the house drain. This view of the
matter is the one that has been adopted by the framers of the
recently - published (October 30th, 1900) London County
Council Drainage Bye-laws, in which the provision of such
intercepting traps is made a sine qua non for every building
situated within the County of London, and may be taken,
therefore, as fairly representative of modern sanitary opinion
to-day. It is true that the intercepting trap is not an
unmixed blessing—not an ideal sanitary appliance, but what
we have to do is to choose between two evils, viz., having
sewer gas laid on to the house, or having the
efficiency of the house drain somewhat interfered with;
and the latter is the lesser evil.
The first principle in house drainage, then, is the intercepting
of the drain of the house from the sewer into which
It discharges, with the object of preventing the passage of