4. Urine does not corrode an iron soil pipe, protected by a coal-tar pitch so- lution or by enamel, more than a lead pipe.

5. The outside of iron pipe can be efficiently protected from rusting by paint, coal-tar pitch or enamel.

G. Lead cannot be caulked into iron, but a good plumber always solders a brass ferrule by a wiped joint to the lead pipe (or trap), and caulks the brass ferrule into the hub of the iron pipe.

7. Any one who will take the trouble carefully to examine the joints of iron pipe, made by an honest and conscientious plumber, will readily admit the possibility of making tight joints with iron pipe. Only iron pipe of a sufficient strength to withstand the knocking occasioned by caulking the lead is used in American plumbing.

But, while iron pipe is fully equal in all the above respects to lead, it has great advantages over it. "Lead soil pipes are very heavy, and, therefore, liable to sag and split open, to have holes eaten into them by rats, and have nails driven into them by carpenters, and also to corrode, and they require much greater skill to put up, and involve more expense; therefore the statements of Hellyer prove nothing, although they demonstrate the absurdity of bricking soil pipes into a wall, and the necessity of so placing them that they are at all times readily accessible for inspection; and also prove what few people seem to realize, that the drainage system of a house requires periodical testing and inspection just as much as a steam boiler or piece of machinery."*

* Bee articles on " Plumbing Practice," In the Sani-Bngineer, vol. 4.

Pipes of wrought-iron, coated with coal-tar pitch, have been lately used for soil pipes, notably in the Durham system of house drainage. I am not prepared to say whether or not such pipes last as long as cast-iron pipes protected with the same coating..

Soil pipes should not, as a rule, be larger than four inches inside diameter; this size will answer for half a dozen or more water closets on one vertical stack of pipe. From a late account of the sewerage of the city of Pullman, near Chicago, I learn that several hundred soil pipes of 3-inch bore were used in the houses, and "in the case of three-story flats, one pipe frequently has six closets connected to it." Very few instances of stoppage occurred, and these were always "due to obstructions that got in during construction, and never to the use of a small-sized pipe." Such a reduction of the size of soil pipes will undoubtedly increase the danger of "siphon-age of traps," and for this reason it is hardly safe to use soil pipes smaller than four inches inside diameter.

Waste pipes of iron should be 11/2 or 2 inches in diameter. This is ample for the waste water of one or more bath tubs, and a large number of wash bowls.

I may here remark that, contrary to the generally entertained opinion, a nearly horizontal or inclined pipe can be kept clean by flushing much easier than a vertical pipe. The flushing water in this latter case soon assumes a whirling motion, and the scattered drops fall downward without exerting much scouring action upon the interior of the pipe. Hence the importance of having the inside of soil and waste pipes as smooth as possible to prevent solid matters from adhering to the sides, where hardly any amount of flushing will take them off.

The arrangement of soil and waste pipes should be as direct as possible. It is desirable that each vertical stack should extend from cellar to roof in a straight line. In planning the plumbing for a dwelling too much care cannot be taken to secure such an arrangement. Every offset, every bend in the pipe forms an obstruction to its proper flushing, with both water and air. Horizontal soil pipes are especially objectionable; the water closets, baths, bowls and sinks should always be located in groups, and as near to their respective pipes as possible.

It is desirable to run soil pipes and waste pipes in sights so that they may be accessible. I decidedly condemn the usual plan of architects of building recesses or niches in the walls for pipes. The difficulty of caulking the back part of pipe joints in this position is very great. Where objection exists to having the pipes in sight, they should be boxed up, but I would always insist upon having the cover fastened by screws, which can be easily removed, and not by nails.

Iron soil and waste pipes should be supported at distances of not over five feet by strong iron hangers or hooks.

Branch pipes should enter the vertical stack by means of a Y or half Y branch, wherever possible; a right-angled junction, by a T branch, is not so objectionable here as in the case of horizontal or inclined pipes.

In badly drained houses, with cheap plumbing work, it is not uncommon to find the joints of pipes made only with sand and paper, or with putty, mortar, cement, sulphur and pitch and red lead, or other material. All of these joints are worthless, and therefore extremely objectionable.

Joints of iron pipe should be made by first inserting a little picked oakum into the socket, care being taken that no part of this gasket enters the pipe. The oakum prevents the molten lead from running into the pipe, where it might form an obstruction to the flow. Molten lead is then poured into the hub, enough quite to fill it. As lead sin-inks in cooling, it must afterwards be carefully hammered with a special caulking tool, thus filling the space between spigot and hub, so as to make a perfectly gas and water tight joint. In order to be able, at all times, to inspect the joints, it is a good practice to leave the caulked lead without a cover of paint, cement or putty, the marks of the caulking tool being thus left exposed to view.

A tight joint can also be made with a mixture of sal ammoniac, iron filings and sulphur. Such "rust joints," however, are not much used for soil pipes.

Where wrought-iron is used for soil and waste pipes, the joints are screw joints, and can be made tight as in steam fitting work.