The House Drainage System

To develop the pattern for a tapering sleeve for a vent for a flat or nearly flat roof, draw, as in Fig. 151, XY at random; set off AB equal to the altitude of the sleeve; then AC from A, perpendicular to AB; then BD from B, parallel to AC; let AC equal half the diame ter of the sleeve at the top, and BD half the bottom diameter; then cut CD with a lire crossing X Y. Lines AC, CD, DB, and BA now out line half the elevation of the sleeve at the center. Next, with the intersection of X Y and CD projected (X in the diagram) as a center, describe the arcs EF and OH. On EF, set off the circumference of the base of the sleeve JK (twice BD X 3.1416), and then indicate JX and KX. This ops the net pattern, and it remains only to add the necessary working edges to get, when cut out and formed up, a sleeve exactly conforming to the shape and dimensions required.

The development of a tapering sleeve for a pitched roof by strictly geometrical methods, is so intricate, and the springs and pitches of roofs so varied, that the plumber usually ignores—and is generally sensible in doing so—the true methods of cutting out such flashings. Lead is pliable; and in lieu of the more tedious method, fiashings for pitched roofs are roughly laid off as follows, and then worked and trimmed to suit.

The circumference and curvature of the top edge and lines of the ends to be joined, are obtained by full-size diagrams in the same way as for a sleeve for a flat roof, shown by Fig. 151. The circumference of the top edge is, in this case, set off on GH, because the bottom, corresponding to JK, is unknown. The elevation A BCD is made just as though a sleeve was to be made for a flat roof, with the tapering side equaling CD, Fig. 152, which should be laid out to represent the elevation of the sleeve desired. The pattern diagram (Fig. 151) should be so drawn as to throw line XCD about the center or neck of the pattern, so as to bring the seam on the low side and thus present solid metal to the flow of water down the roof. The line of dots marked Z in Fig. 151, approximately outlines the bottom of the pattern. The cross-mark guides by which to draw the bottom of the flashing, are seldom more than five in practice, and their positions are determined in this way: JX and KX of the pattern diagram are extended and set off from the GH line equal to XK, Fig. 152. This gives the actual seam length for the low side of the flashing, as would be indi cated if XJ and XK, Fig. 151, were ex tended to cut the extremes of the cross mark guide line. CD of both the ele vation and pattern diagram being equal, CD, Fig. 151, equals the length of sleeve in the neck or upper side. For the

length of sleeve at the sides, half way between the neck and seam, produce dotted line K' Y, Fig. 152, parallel to CX, to a point where it will intersect the roof-plane at the center of the pipe space. KIX will then be equal to the required side lengths of sleeve, and may be set off on the pattern diagram by pro jecting radii from X, cutting the pattern midway between C and the seam lines, and setting off the distance XK' on these radii, measuring from the GH line. These specific points are a sufficient guide for laying out the bottom in any ordinary case.

Trap Ventilation.

Needless multiplication of soil and vent connections may lead, in some cases, to conditions fully as deplor able as any that would follow the primitive simplicity of olden times. There are, however, certain principles that must be carried out to secure a perfect working job. These have often been cur tailed by the extremists of one class, and always at the expense of the quality of the work. It is the extremists who regulate progress and keep things at a reasonable mean. The extremists in progression would drag us into practices perhaps unsafe; while their opposites, derisively termed "old fogies," hold us back, sometimes on untenable ground. The result is that the conservative element is the safest class to follow; it neither discards a well-tried method nor embraces a new one, without good reason to sustain the action. As before intimated, the change in character of buildings and mode of life has necessitated a maze of pipe work in some buildings, which to the uninitiated looks like a senseless network thrust on the owner to the pecuniary gain of the plumber. This is not the case, however, as every plumber well knows; and there is no better way to disarm this type of credulity than for the plumber to be well versed in the philosophy of his business.

The familiar cry that crown ventilation of traps destroys the seal by evaporation, is often but the echo of the voice of a man with an axe to grind. The deep-seal trap costs but a trifle more than the ordinary. There are also positive mechanical means—comparatively cheap, too—of protecting a vacant or unoccupied house against sewer air. In occupied houses, there is no chance for traps to lose the seal by evaporation; and, when properly piped, the evaporation of seals does not take place so fast as might be supposed. The crown vent is merely, or should be, to keep the water from being siphoned out of the trap. It is the practice of making the crown vent do duty not only as a siphon-preventer but also in the capacity of a stack vent, that has created the impression as to rapid evaporation.