“Flushing-gates,” an engineer has reported, “are chiefly of use in sewers badly constructed and without falls, but containing plenty of water; and they are of very little use where the gate has to be shut 24 hours and longer, before a head of water has accumulated; but where intermittent flushing is practised, strong smells are often caused solely by the stagnation of the water or sewage while accumulating behind the gate.”
The most general mode of flushing at present adopted is not to keep in the water, &c., which has flowed into the sewer from the streets and houses, as well as the tide of the river, but to convey the flushing water from the plugs of the water companies into the kennels, and so into the sewers. I find in one of the Reports acknowledgments of the liberal supplies granted for flushing by the several companies. The water of the Surrey Canal has been placed, for the same object, at the disposal of the Sewer Commissioners.
It is impossible to “flush” at all where a sewer has a “dead-end;” that is, where there is a “block,” as in the case of the Kenilworth-street sewer, Pimlico, in which five persons lost their lives in 1848.
There is no difference in the system of flushing in the Metropolitan and City jurisdictions, except that for the greater facilities of the process, the City provides water-tanks in Newgate-market, where the heads of three sewers meet, and where the accumulation of animal garbage, and the fierceness and numbers of the rats attracted thereby, were at one time frightful; at Leadenhall-market, and elsewhere, such tanks were also provided to the number of ten, the largest being the Newgate-market tank, which is a brick cistern of 8000 gallons capacity. Of these tanks, however, only four are now kept filled, for this collection of water is found unnecessary, the regular system of flushing answering the purpose without them; and I understand that in a little time there will be no tanks at all. The tank is filled, when required, by a water company, and the penstocks being opened, the water rushes into the sewers with great force. There is also another point peculiar to the City—in it all the sewers are flushed regularly twice a week; in the metropolitan sewers, only when the inspector pronounces flushing to be required. The City plan appears the best to prevent the accumulation of deposit.
There still remains to be described the system of “plonging,” or mode of cleansing the open sewers, as contradistinguished from “flushing,” or the cleansing of the covered sewers.
“When we go plonging,” one man said, “we has long poles with a piece of wood at the end of them, and we stirs up the mud at the bottom of the ditches while the tide’s a going down. We has got slides at the end of the ditches, and we pulls these up and lets out the water, mud, and all, into the Thames.” “Yes, for the people to drink,” said a companion drily. “We’re in the water a great deal,” continued the man. “We can’t walk along the sides of all of ’em.”
The difference of cost between the old method of removal and the new, that is to say, between carting and flushing, is very extraordinary.
This cartage work was done chiefly by contract and according to a Report of the surveyors to the Commissioners (Aug. 31, 1848), the usual cost for such work (almost always done during the night) was 7s. the cubic yard; that is, 7s. for the removal of a cubic yard of sewage by manual labour and horse and cart. In February, 1849 (the date of another Report on the subject), the cost of removing a cubic yard by the operation of flushing, was but 8d. This gives the following result, but in what particular time, instance, or locality, is not mentioned:—
| 79,483 cubic yards of deposit removed by the contract flushing system, at 8d. per cubic yard | £2,649 |
| Same quantity by the old system of casting and cartage, 7s. per cubic yard | 27,819 |
| Difference | £25,170 |
“It appears, therefore,” says Mr. Lovick, “that by the adoption of the contract flushing system, a saving has been effected within the comparatively short period of its operation over the filthy and clumsy system formerly practised, of 25,170l., showing the cost of this system to be ten and a half times greater than the cost of flushing by contract.”