179. Lead pipes 2 inches in diameter and less, which run against walls, etc., are usually supported by means of flanges, or pipe tacks, which are soldered on to the pipe at convenient intervals, and are fastened to the walls with common wood screws, as illustrated in Fig. 65, which shows a 3/4-inch lead pipe a secured to a wall or pipe board b by molded pipe tacks c, c and 1-inch wood screws d, d.

Fig. 65.

Fig. 66.

The tacks are made of old lead, slightly hardened with a few old wipe joints mixed in. They are cast in brass molds.

180. Pipes over 2 inches in diameter are best supported by means of broad bands, such as shown in Fig. 66, which are attached at intervals of about 3 or 4 feet. The width of the bands, along the line of the pipes, measured for pipes of 2, 3, or 4 inches diameter, should be about 6, 8, or 10 inches, respectively. An oblong hole c is cut in the front of the band, and is filled with hot solder and wiped to the face of the pipe. The side flanges of the band are wiped to the face of the pipe, as shown at b. The band is shown secured to a stone wall by flat-head spikes a, driven into wooden plugs d, which have been previously driven into holes cut into the stonework.

181. If the temperature of a lead pipe, which is supported by rigid fastenings, is maintained nearly uniform, as is the case of the cold-water supply pipes, the pipe can only be changed in form by its own weight, the jarring of the building, etc. If, however, the temperature of the pipe is variable, as is the case of the pipes which supply hot water to the plumbing fixtures, the pipes will expand as the temperature increases, which causes them to bulge between their supports. Lead is so very low in elasticity that when the pipe becomes cool, the sags are not entirely taken up by contraction; and upon every application of heat, the sags will increase in size, particularly on horizontal pipes, until the lead becomes so thin near the points of support as to cause a leak. The leak generally occurs in a crack which is formed around that part of the pipe near the tacks.

Suppose that a lead waste pipe 2 inches in diameter, secured in a vertical position against a wall by hard-metal tacks or lead bands, has a kink in it, and that hot water passes through the pipe periodically. It will be found that since the kink is the weakest part of the pipe, it will take up most of the expansion between the tacks on each side of it. This action subjects the kink to a cross strain, repetitions of which will soon overcome the cohesive strength of the lead and cause the metal at that point to crack. Kinks should be carefully avoided in all lead-pipe work. A kink in a lead waste pipe is a positive sign of slovenly, careless, or ignorant workmanship, and should not be tolerated.

182. When a hot-water pipe runs horizontally, it is better to support it upon a continuous ledge or shelf. It should have room enough laterally to bend and creep, and should be kept from working off the shelf by a suitable rim or flange along the edge of the shelf.

Lead pipes should not be supported by iron wall hooks or similar supports, unless they are protected by an extra thickness of sheet lead between them and the iron, because the edges of the iron will gradually cut into the lead and thus weaken the pipe.

183. The approximate spacing for tacks on lead pipes is given in the following table: