720 



SANITARY SCIENCE. 



alternate exposure of the metal to air and 

 water, by the change of level in the contents 

 of the well, often occasions rapid corrosion. 

 As a substitute for lead in such situations, 

 block-tin pipe presents the most advantages, 

 being little subject to corrosion and harmless in 

 most of its combinations, even if chemical ac- 

 tion should take place. Next to this, tin-lined 

 pipe, if properly made and put together, is 

 most serviceable. Brass pipes, which might be 

 used as suction-pipes, but rarely are, are proba- 

 bly acted upon by the water ; but it is uncer- 

 tain whether the corrosion would, with most 

 waters, injure to an appreciable extent the 

 quality of that which passed through it. Gal- 

 vanized iron pipe, though cheap, is not dura- 

 ble, the zinc coating being soon corroded so as 

 to expose the iron to rust, while the dissolved 

 particles of zinc are carried away in the water 

 and injure its quality, although it is doubtful 

 whether they are absolutely poisonous. En- 

 ameled iron pipes, as found in the market, 

 are quite as durable as the galvanized ones, 

 and impart nothing to the water worse than 

 a slight flavor of coal-tar, which comes from 

 some of them while new. In Germany 

 wrought-iron pipes, coated with magnetic ox- 

 ide by the Bower-Barff process, have recently 

 been put in for service-pipes; and if they 

 prove durable, they would seem to be the best 

 yet introduced. 



Modern Improvements. In ordinary dwellings 

 these are less common in Great Britain than 

 in the United States. Baths with hot and 

 cold waters, found in most American town 

 houses, are there luxuries for the few. Sewer- 

 gas is, therefore, not so prevalent abroad as 

 unventilated cess - pools and broken drains 

 leaching into the soil. At the same time lead, 

 which has always been employed abroad as a 

 material for soil-pipes, is easily corroded by 

 gases, or injured by the gnawing of rats, or 

 other causes, so that baleful consequences to 

 life and health have resulted. In 1873 Dr. 

 Andrew Fergus, of Glasgow, first publicly 

 drew attention to the liability of lead soil-pipe 

 to be thus injured, and exhibited specimens of 

 such corrosions. As a protection against this 

 contingency, the plan was generally adopted 

 of extending all soil-pipes upward through the 

 roofs of buildings and leaving the ends open to 

 the outer air, so as to give the foul gases free 

 vent. This may be called the first and most 

 important step of progress in modern plumb- 

 ing ; and while in this country lead soil-pipe 

 is no longer used, cast-iron having been substi- 

 tuted, the same precaution is still taken and 

 is made obligatory wherever laws regulating 

 plumbing are enforced. At first these vent- 

 pipes were made very small, it being assumed 

 that a slight opening would permit the foul 

 gases to escape. Even now, many plumbers 

 are content to employ a half- or three-quarter- 

 inch vent-pipe, when it is manifest that the 

 friction, particularly if there are many bends, 

 would be so great as to render it almost useless. 



Gas -pipe is still employed for this purpose, 

 though it is apt to be choked by rust caused by 

 the moisture rising from the house-drain. This 

 moisture, when condensed, is liable to freeze 

 and to close the end of the vent entirely, so 

 that plumbers and engineers have gradually in- 

 creased the size of the " stench-pipe " until now 

 it is made of the full area of the soil-pipe, and 

 in the best practice the upper end is enlarged 

 so as to be a fourth or fifth greater. Further- 

 more, the end, instead of being closed by some 

 form of cowl or cap, under the pretense of 

 lessening the stench or keeping out rain, snow, 

 or other obstacles, is now left wide open, the 

 only barrier being a fine wire strainer to pre- 

 vent birds from nesting in the pipe. 



The second step of improvement was in the 

 direction of trapping fixtures. At first it was 

 thought sufficient to place a single trap on a 

 water-closet, and to connect baths, basins, slop- 

 sinks, and other adjacent fixtures with this 

 trap. But it was found that foul odors were 

 evolved from the central trap and passed 

 through the unguarded outlets, while in case 

 of the building settling, or the waste connec- 

 tions sagging, these pipes became mere " elon- 

 gated cess -pools," and in themselves were 

 sources of danger. The plan wa, therefore, 

 adopted of placing an independent trap upon 

 each fixture, however small, and this is now 

 the universal practice. As a further precau- 

 tion, a trap was placed at the foot of each soil- 

 and waste-pipe, to disconnect the latter from 

 the street-sewer, or this barrier would be lo- 

 cated at the front wall of the house. These pre- 

 cautions, however, failed to give complete re- 

 lief. While the sewer-ai'r was excluded from 

 the drainage system, the traps on the house- 

 drain accumulated grease and other foul mat- 

 ter, and the whole lower end of the house- 

 drainage system became filled with stagnant 

 and foul air, which was liable, when displaced 

 by the discharge of any volume of fluid matter 

 into it, to be forced out at some lower fixture. 

 Again, the open soil-pipe at the top of the roof 

 did not serve its intended purpose so long as 

 there was no entrance of fresh air at its foot. 

 An empty bottle will not ventilate itself, how- 

 ever large the mouth may be ; two openings 

 are indispensable for perfect ventilation. The 

 practice was therefore introduced of carrying 

 an air-inlet from a point just inside of the 

 trap on the main drain, either to the level of 

 the ground outside of the house, or by an up- 

 right pipe to the roof. A perfect circulation 

 of air in the whole drainage system was thus 

 obtained. The outer atmosphere being heavier 

 than the drain-air, which was heated by steam 

 from the kitchen - boiler and by the general 

 warming apparatus of the house, there would 

 be of necessity a constant draught in at the air- 

 inlet, and thence along the house-drain and 

 upward through the soil - pipe' to the roof. 

 Careful tests have shown that this action takes 

 place continuously, excepting in damp, muggy 

 weather. Even should the movement be re-r 



