View report page

39
Dr. Butler has pointed out some of the objections to the trap,
and he states that " probably the most universally objectionable
feature of the siphon is that it prevents the efficient ventilation of
the sewers. That the public sewers are inefficiently ventilated in
those cases where their communication with the soil-pipe ventilators
of the house drains is intercepted, is shown in many ways. It is a
common experience with municipal officers that daily complaints
are received, during the summer months, of the offensive smells
proceeding from the openings of the sewers in the crown of the
roadway, placed there originally with the intention of acting as
fresh-air inlets to the sewers, and now in many districts being sealed
off because they are found to act as vents for the foul gasses of an
unventilated sewer."
The other objections to the trap are its liability to obstruction
and the difficulty of obtaining conditions under which it is selfcleansing.
1,725 interceptors were examined in Acton between the months
of May and November, 1907, and of these 124 were found to be stopped.
There were 30 other drains in which the manhole was foul,
a condition which showed that a stoppage had previously occurred
in the trap. Out of the 124, 58 of the stoppages were due to
the cap of the raking arm having fallen on to the channel pipe.
In addition to these, in 167 of the interceptors there was no cap to
the raking arm ; either it had not been fitted on at the time the drain
was constructed or it was subsequently removed.
Whatever may have been the original cause, in 225 cases, or
13 per cent, of the drains examined, the interceptor, apart from other
defects found, failed in its object, and the sewer air had access to
the house drains. The result was that the untrapped opening
which had been intended as the inlet ventilator of the house drain
acted as the outlet ventilator of the sewer. It is true that a mica
flap is usually fitted into the inlet pipe, but the flap gets out of
repair frequently, and thus fails in its object. To such an extent
is the inlet ventilator recognised as a source of nuisance that it is
not an infrequent event to find the inlet pipe stopped by the tenants