465
27
Assuming that, in accordance with common opinion, street sewers have to be ventilated, the most efficient way of so doing has to be considered. In my opinion, the best way is to make every house-sewer and ventilating-pipe a sewer- vent or ventilator, by omitting the intercepting-trap of the house-sewers. Mr. CROOK, when I last met him, informed me that he had done so, in several cases. This system is common, indeed, almost universal, in America.. Several local Autho- rities, in England, have adopted this plan, and a large number of experts are in favour of it. I have adopted it, in the case of Kingston, Jamaica, and Port Louis, Mauritius, and further, have decided to do so, in the case of Port of Spain, Trini- dad. In the two first-named places, the works have been in operation for some years, and I have heard no complaints concerning this manner of ventilation, or more properly, Venting.
of combined
77. In the case of Hongkong, an objection may be raised to this system of Application combined House and Street Sewer ventilation, on account of the great differences of ventilation level, which exist, between contiguous dwellings. The mouth of a given ventilat- street sewer ing pipe will often be near to, and at the same level as, a neighbouring dwelling- kong.
room.
ance.
I do not, however, consider that this is an objection, of great practical import- The number of ventilating-pipes would be so great, that the nuisance, from each, would be inappreciable. It is to be remembered that sewer-air will not be continually pouring out of all and sundry ventilators, like smoke from a chimney. The air will be going down some, up others, according to wind, temperature and various other conditions. The diffusion and dilution will be so great as to prevent any appreciable nuisance. At any rate, the nuisance will be less than that due to the untrapped gulleys or gratings in a street or lane;, often narrow and surrounded by lofty houses. Again, every house-sewer of any length is, or ought to be, provided with a ventilating-pipe, which will, from time to time, emit stenches, and which, I maintain, will generally be quite as offensive as if the house-sewer were one in uninterrupted communication with the street-sewer, possibly more so, on account of inadequate flushing of the house-sewers.
The main point to be considered is whether there are sufficient house-venti- lators, to bring about the desired end. In the case of new Chinese houses, erected according to the laws now in force, or which, it is to be hoped, will shortly be in force, there will be practically no house-sewers. The sewage flows from the back- yards, into an open channel, in the back-lane, which discharges into a trapped-gulley, connected with the street-sewer direct. As there is no house-sewer, there is no ventilating-pipe. To carry out the idea, in such cases, it would be necessary to take power to erect ventilating pipes, against the houses, or elsewhere.
78. The question of Sewer Ventilation is one of the utmost difficulty, and con- cerning which no two authorities agree. Probably no one system is capable of universal application. Therefore, I recommend tentative procedure. The City of Victoria is sub-divided into several districts, each having its special outfall. Let one district be taken in hand. Let the sewer-gulleys be trapped; using improved traps, as suggested by the Director of Public Works. Let the gratings of the manhole- covers be stopped up, and above all, let the heads of the sewers be connected-up, as described in paragraph 75, then see what happens.
If any inconvenience occurs, owing to traps being forced, or otherwise, then let arrangements be made for the provision of Vents. My opinion is that these should be numerous and small, and above all, as inconspicuous as possible. Cast- iron pipes, of from four to six inches in diameter, carried up the sides of houses, just above the roof-gable, will in most cases be best.
A conspicuous ventilating-shaft is always assumed to vomit forth stenches, whether it does so or not. I remember a case in Malta, where a ventilating-shaft,
of house and
to Hong-
!
Recommend- ventilation.
ation, as to