Having shown simple ways in which offensive or dangerous gases may be securely trapped off and debarred from entering the house through the various fixtures at their points of connection with the water and soil pipes, it now remains to provide against a possibility of leakage in the drain pipes themselves, for if these are unreliable and badly jointed all our pains with traps and fixtures will be of little use.

The term "soil pipe" is, by custom, applied to the perpendicular portion of the main waste pipe. The horizontal part is called the "drain pipe."

The Material and Methods of Jointing. The material for our pipes naturally forms the first subject for consideration, inasmuch as upon it their proportions, treatment and arrangement in a great measure depend.

By far the most suitable material yet discovered for soil and house drain pipes is iron, and the most important matter connected with its use is the formation of the joints between the separate pieces.

Soil And Drain Pipes 484

Lead has been almost entirely abandoned in this country for soil and drain pipes, on account of its want of strength and elasticity; its comparatively high cost; its liability to be perforated by vermin, nails or corrosion; and of the greater time and labor required to make the joints. Large lead pipes often sag of their own weight and tear away at their points of support. The action of alternate hot and cold water also produces a destructive effect upon the material. It expands under the influence of heat, but does not return again to its original dimensions, and accordingly it can be said to undergo perpetual change, creeping constantly from its original position; and unless held in place by special provisions it would undoubtedly in time walk off by itself out of the premises altogether. Good stories are told of old leaden roofs which have crept entirely off the building and fallen into the street.

S. Stevens Hellyer said in one of his early publications in comparing lead with other materials for soil pipes: "This may seem a curious question to ask of plumbers; as well ask a shoemaker of what material should boots and shoes be made! Everybody knows that the latter would say, "There's nothing like leather,' as the former is sure to say, 'There's nothing like lead.' * * * Allowing experience to be my schoolmaster, I answer lead, especially for our climate." Mr. Hellyer claims the following points of superiority for lead: Its greater smoothness; great resistance of corrosion; greater ductility for bending to suit the various positions it has to occupy; more perfect joints; greater adaptability for connecting with branch wastes; and greater compactness, which allows it to be placed in slots or niches smaller than those which are required for iron. He admits the following objections: Its deterioration under alterations of temperature which tend to work it until it breaks; its sagging; its expensiveness; its liability to be perforated by rats or carpenter's nails; its greater weight; and the requirement of greater skill in making the joints.

The advantages which Mr. Hellyer claims for lead have within late years lost their force. Improved methods of protecting and jointing other materials have placed them in these respects far ahead of lead, as will be shown hereafter. White enamel is now applied to cast iron in such a manner as to render the surface as smooth as that of new lead, and this art has been serviceable particularly in bath tubs and other fixtures, though it is also used in piping. But in use lead soon loses its smoothness and the sewage adheres to the surfaces of the pipe to a greater or less extent and roughens it, in time, with a hard deposit of greater or less thickness according to the usage of the pipe, so that the difference in smoothness at the outset in favor of lead as compared with our iron pipe is of small consequence after a few years' use. The numerous cast bends and fittings now made and adapted to every possible turn or angle liable to be encountered in arranging the pipe renders the ductility of the lead pipe no longer of any advantage. Finally, other and more suitable materials are now joined in such a manner as to render them quite as compact as the lead pipe.

Stone and brick drains cannot be effectively flushed, on account of the roughness of their interior surfaces. Moreover, they are porous to a certain extent, and the cement with which they are laid is always more or less pervious to waste.

Copper is easily corroded by the acids of decomposition, and is, moreover, too expensive except for exceptional cases which need not be considered here.

Zinc, tin and galvanized sheet iron are totally unsuitable and not to be considered for a moment. In the worst kind of "jerry buildings" they are, however, occasionally used.

Cast and wrought iron are the materials which are now generally used, and they have proved themselves for this purpose the best. They are light, cheap, stiff and strong and they corrode so slowly that if of the proper thickness they will last as long as the house itself is likely to.

The experiments of M. Gaudin, made in 1851, show the maximum rate of loss by rust of uncoated cast iron pipe exposed to the action of clean fresh water on both sides to be a little over an eighth of an inch per century. His experiments extended over a period of thirteen years. With the present method of protecting iron its life can be very greatly prolonged, indeed even the use of the ordinary bituminous coating (coal tar pitch) has proved, when it is properly applied, to be able to keep the pipe quite intact under certain conditions for twenty years. The life of a soil pipe, even when quite thin and uncoated, has been found by experience to be so great that it is not unreasonable to suppose that the greasy matters contained in house drainage serve to protect the pipe in a measure from the acid components of the sewage.