Every sewer is more or less exposed to intermissions in the flow of
the water that it leads, and the result is a diminution in velocity
which leads to deposits of solid material. Hence the necessity of
regularly flushing the sewer with water, which removes from the sides
the substances that have attached themselves thereto, and which,
without such precaution, soon decompose. In a word, it is necessary
that a _perfect_ washing shall be assured, and this can be done only
by heavy rains or by strong currents of water. As regards rain, that
could not be relied upon; and to have a force of men specially charged
with the service of washing, that would be too costly, and so recourse
has been had to automatic apparatus.
[Illustration: FLUSHING RESERVOIR.]
The automatic siphons used for flushing sewers are characterized in
general by the presence, at the base of the discharge branch, of a
fixed or movable receiving vessel full of water. This vessel has the
inconvenience of breaking the effect of the charge, and the result is
that these apparatus do not render the services that might be expected
from them. Some of these apparatus have valves, floats, chains,
pulleys, and levers. These are still more defective, since their
operation is delicate. The parts of which they are composed easily get
out of order, and then the reservoir does no more flushing at all. A
good automatic flushing reservoir must therefore be of the greatest
simplicity, and its parts must be fixed and strong, and the outflow of
the water must be rapid and energetic and directly from the reservoir
into the sewer. In a word, its construction should be such that there
shall be no need of inspecting it, and that its operation be regular.
The apparatus devised by Mr. E. Putzeys, Director of Works of the city
of Verviers, well fulfills the conditions of an excellent flushing
reservoir with an automatic siphon. The siphon has a double curve, but
may, however, have different forms according to the various uses for
which it may be employed, such as for flushing sewers, urinals,
closets, etc.
The annexed figure represents the apparatus as arranged for flushing a
sewer. The apparatus operates as follows: In the bottom of the branch
of the siphon, S, there is always some water, so that, during the
filling of the reservoir by means of the cock seen in the figure, the
air is compressed in the branch S to a degree that cannot exceed the
pressure of an equal height of water to about double the height of the
siphon. The reservoir therefore can continue to fill without the water
escaping.
The submersion of the small siphon, a, b, c, is less than that of the
principal siphon, S, and it follows that when the level of the
reservoir reaches a height equal to b, a, a new influx, however small
it be, causes the discharge of a few drops of water from the auxiliary
siphon, a, b, c, which is always full of water. At this moment the
water that it contains can no longer resist the thrust of the
compressed air in the branch of the siphon, S, and is therefore
forced, along with the compressed air, into the flushing pipe.
By virtue of the principle of communicating vessels, the water of the
reservoir tends to resume its level in the interior of the apparatus,
and it then enters with such impetuosity that the siphon, whatever be
its dimensions, is primed. The entire reservoir empties
instantaneously, and the water flows to open the sewer.
From the experiments made at Verviers by the inventor, it results
that, with a pipe 10 inches in diameter, the emptying of a 175 cubic
foot reservoir can be effected in 30 seconds.
We may remark that with this apparatus we obtain the maximum of useful
effect, seeing that the work developed is represented by the total
head of the water diminished simply by losses of charge due to
friction in the pipes. In other apparatus the loss of charge is much
less, since the flushing is broken by a receiver.
Putzeys' apparatus, therefore, with a much less discharge of water, is
capable of producing an effect superior to that of similar apparatus.
On account of its simplicity and plain character, there is no need of
precision in the installation of this apparatus, and horizontality,
even, is not a _sine qua non_ for its perfect operation.
The siphon is very easily cleaned, and this is a great advantage,
since it permits of utilizing sewage matter for filling the flushing
reservoir.--_Chronique Industrielle._
* * * * *