FURTHER CRITICISM OF THE SEWERAGE SCHEME.

Gisborne Times, Volume XXX, Issue 3570, 9 July 1912, Page 2

FURTHER CRITICISM OF THE SEWERAGE SCHEME.

(TO THE EDITOR.) Si i - ,—-Again I ask permission through your valuable paper to point out to the ratepayers of Gisborne an important fact which only the few with a knowledge of sanitary plumbing and drainage can guess the full importance of. The sewerage scheme which has been designed for Gisborne is the only one, with one exception (namely Timavn designed by the same engineer) which after enquiry I find has no intercepting trap. The purpose of this letter is to point out the very real danger which may arise from the omitting of this important fitting to house servif.es. It may be pointed out that drain air is practically harmless, but sewer gas is the product of the putrefaction of animal matter, which on decomposing liberates certain gases, amongst which are carbonic acid, sulphuretted hydrogen, sulph. ammonia and free ammonia. These being of a noxious character are known to give rise to mephetic poisoning.

Another danger is from aerial infection to those who may be residing in dwellings where the vent shafts from the sewer may be exposed to the sun rays for a considerable portion of the day. For instance, if there was a case of fever or other infectious disease in a dwelling where the vent pipe may be on the shaded side of the dwelling, then this vent would act as an inlet for the fresh air, but the adjoining house having the vent pipe exposed to the sun rays, which by heating the air in the vent pipe rarities it and sets up or creates a. current of air from the spwer from which it draws the germs ol enteric or other zymotic fevers which are passed into it from the dwelling whose vent pipe is protected from the sun. Thus it will he seen that the occupants of the house with the vent pipe exposed to the sun are in danger of infection from any germs which may be' disseminated by the sewer gas. It may be said that the vent is carried high enough above any windows to allow the gases to disperse, but it must be remembered that sewer gas contains a large quantity of carbonic acid and lias a greater specific gravity than air, therefore, when it issues from the top of the vent pipe into the colder air it descends rapidly before diffusion takes place, thus allowing probably only a small but still a dangerous quantity of the gas to be diffused into the dwelling. _ With drain air, the quantity of noxious gases are- not nearly so great, therefore not so heavy, and diffusion takes place more rapidly, thus lessening the danger which is incurred by connecting the drain direct to the sewer without the intervention of an intercepting trap.

Three facts can be proved by an ocular demonstration which would convince the simple-minded layman, a demonstration which the ratepayers may have if they evince sufficient interest in their own health as to care to see it. f should here like to quote E. Thomas Swinson, 11. P., W.R.San.I. Lecturer on Sanitary Engineering, etc-, etc. :

“The experience of the last few years lias conclusively demonstrated that traps are not fads, hut necessities. At the present time it is the fashion in a limited circle—mostly composed of local surveyors —to decry intercepting traps. They desiguate them obstructions, and would doubtless be very glad to see them abolished altogether, owing to the impediment which they impose against the ventilation of the public sewers through tlie house drains belonging to private o\\ ners. Regarding the subject from an opposite standpoint, the sanitarians object to the house drain being used as the medium of discharge for the noxious gases generated in the sewers, owing to tlie risk entailed upon the occupants of the house in the event of a defect occurring in the untrapped drain, or in the ventilating pines or soil pipes directly connected to it.”

Tn Great Britain the duty of ventilating the sowers is one that devolves upon the public authorities under the Public Health Acts, and it is unfair that the sanitary authority should attempt to impose this duty on the owners of dwelling houses as they are doing here in Gisborne. Again, Mr Geo. E. Evans, a wellknown authority, says:—

“It is sufficient to say that until every house has a drainage system, absolutely proof against the escape of sewer gas into the house, a disconnecting trap is a necessity.”

There can be no absolute proof against the escape of sewer gas into houses with putty joints on any fittings such as we have at present, there always being the danger, although those joint may he left perfectly tight, of them being broken by receiving a blow from many causes. .

Sufficient Ims been said to point out tin necessity for an intercepting trap being used that necessitates such a stringent by-law as the one represented bv tire Borough authority’s Bylaw iSo. 1. I am, etc.., EXPERT. Gisborne, July 6, 1912.