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173
is collected by pipe and brick drains laid on the floors of the
basins and led by conduits to the well of the pumping-engine.
The thickness of this filtering media ranges from eight feet in
the case of the Chelsea Company to two feet nine inches in that
of the Grand Junction Company. The thickness of the upper
layer of sand, which is the most effective of the layers, varies
from two feet to four feet six inches. The sand becomes clogged,
in course of time, and then the upper layer is scraped and
removed. Renewals of sand take place periodically as the layer
becomes reduced below an assigned minimum. The West
Middlesex Company is spoken of as prominent "in respect of the
uniformity in the quality of its water," probably due to the fact
that it "uses to an exceptionable extent for filtering purposes
sand from Harwich and its neighbourhood, which is remarkably
fine and uniform in grain."
But filtration avails little if the water is allowed, as
frequently happens, to be fouled in the cisterns ; whether through
the uncleanly condition of those receptacles or by the connection
of them with drains through the medium of "waste-pipes," which
the Companies only have the power to abolish, viz., under the
provisions of the 14th water regulation, which reads as follows:—
Regulation 14.—"No overflow or waste-pipe, other than a warning pipe,
shall be attached to any cistern supplied with water by the Company,
and every such overflow or waste-pipe existing at the time when these
Regulations come into operation shall be removed, or at the option of the
consumer shall be converted into an efficient 'warning-pipe,' within two
calendar months next after the Company shall have given to the
occupier of, or left at the premises in which such cistern is situate, a
notice in writing requiring such alteration to be made."
Sir Francis Bolton remarked that—
The particular object of the above regulation is to prevent the waste of
water ; but if the overflow-pipe is brought outside the house, and the end left
exposed to the air, instead of being carried into the drain, as is often the case,
it will effect an object of far greater importance, by getting rid of the poisonous
effluvia and gases from the drains; which would otherwise ascend through the
pipe, and not only be partly absorbed by the water in the cistern, but be partly
mixed with the air in the houses, thereby becoming a cause of fever and
disease."