from some of the faults of rolled lead, but practical plumbers would prefer rolled sheet for any purpose. Cast lead is specified occasionally, and then the plumber may make it himself from the waste lead and clippings of his workshop. A strong table with a smooth top, having raised edges, is required. This is covered with a layer of fine dry river sand, perfectly level and smooth. The molten lead is poured into a heated oblong trough, fixed across the table; the metal is poured thence in a wide stream upon the sand as evenly as possible; a wooden roller is rested on the raised edges and pushed quickly along, spreading and driving forward the lead, and leaving an even uniform thickness behind on the table to cool. <Callout type="important" title="Important">Practical plumbers would prefer rolled sheet for any purpose.</Callout> 458 DOMESTIC SANITARY DRAINAGE AND PLUMBING. Cast sheet lead should never be made of less thickness than eight pounds to the foot, as it is liable to be irregular and to contain minute sand or air holes or flaws. Milled lead is first cast in an iron mould into plates about six feet square and six inches thick. It is lifted by a crane upon the rolling mill, where it is drawn in by small reversible rollers under heavy metal cylinders, the upper cylinder being supported on regulating screws to relieve the lead at first from too great a pressure, and to enable the workman to lower the cylinder gradually as the sheet becomes thinner. As the lead passes through, under pressure between the metal cylinders, it is compressed and elongated. A long bench of rollers receives €md carries along the sheet over a bench as it passes back €md forward, the top cylinder being allowed to descend more and more each time by a turn or two of the regulating screws. The workman is able to judge when the requisite thickness of sheet has been attained by merely measuring the length of the sheet. The 6-feet square piece of lead may be lengthened by this process into a sheet of lead from two hundred to four hundred feet long, according to the thickness. The usual market thicknesses of rolled sheet lead are 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 lbs. per superficial square foot; but lead can be rolled much thicker. The sheets usually measure 25 feet to 35 feet long, by 6 feet to 7J feet wide. <Callout type="tip" title="Tip">Lead pipes were formerly cast in short lengths of considerable thickness.</Callout> The lead manufacturers prefer to sell their sheets the full width as it comes from the mill. For aprons or flashings 3-lb. lead is always too light ; in any exposed position 5-lb. or 6-lb. lead should be used. Boof -flats and gutters require at least 7-lb. and 8-lb. lead ; hips and ridges, at least 6-lb. and 7-lb. lead. Much heavier lead may be used with ultimate advantage in exposed positions and in all high-class work. The weights of sheet lead may be known by the thickness : PLUMBERS' MATERIALS. 459 yV of an inch = 3 lbs.; ^, 4 lbs.; ^, 5 Ibe.; ^, 6 lbs.; i, 7 lbs.; A, 8 lbs.; |, 9 lbs.; A, 10 lbs.; A, H lbs.; i 12 lbs.; i 15 lbs. On the Birmingham wire-gauge the various thicknesses of lead should barely enter the gauge very tight at the following numbers : 3 lbs., 18 ; 4 lbs., 16 ; 5 lbs., 14 ; 6 lbs., 12; 7 lbs., 11; 8 lbs., 10; 9 lbs., 9; 10 lbs., 8; 11 lbs., 7; 12 Ibe., 6. Architects, surveyors, and master plumbers, by carrying with them a pocket gauge, can thus easily and effectually check the weights of lead laid down on a building. Lead pipes were formerly cast in short lengths of consider- able thickness, the bore being made the size required, and the pipes being afterwards drawn out and reduced to any desired weight and strength. The hydrostatic press now produces lead pipes perfectly finished in long lengths ; they are pressed out from a cylinder of molten lead through a die or mould of any diameter, and are coiled round revolving drums. The sheet and pipe lead used in Dublin contains an ad- mixture of three parts tin, which effectually checks the chemical action on the pure water with which Dublin is supplied. For use with all pure soft waters this alloy should be used. With reference to tin-lined lead pipe the writer has not much experience, but the making of wiped joints, owing to the fusible nature of tin as compared with lead, must be a very great difficulty, lead not melting till 617', while tin melts at 442^ Professor Frankland said the public should be warned against the use of tin-lined lead pipe. In some cases, he states, the two metals produced an alloy which acted more on the water than lead pipes alone, and caused danger. The composition lead piping used for gas distribution is made of scrap lead and antimonial lead, which contains impurities rendering it dangerous to employ it for water distribution ; it is usually very hard, and is made thin and light. This piping is frequently tinned when leaving the press, adding about six shillings a ton to the cost. The tin is applied to the lead from a cup round the die from which the tubing rises. Tin is one of the oldest, as it is one of the most useful and beautiful of metals. It is obtained from an ore called tin stone, usually found in veins running through primitive rocks, in Cornwall, Malacca, Banca, Mexico, and Australia. It is sometimes found in a very pure state in alluvial soils where it was carried by water and deposited; it is then called stream tin. The original veins can be generally traced out by following up the likely course taken by the stream. The metallurgical operations to extract the metal from the ore somewhat resemble those in the case of lead ores — ^stamping and washing, to remove the earthy and lighter portions; roasting, to decompose pyrites and get rid of arsenic and sulphur; washing, to dissolve cupric sulphate and carry off ferric oxide; reduction, to separate the tin from oxygen and earthy matter ; and refining, or liquation, to purify for use. In the latter operation the tin is heated till it begins to fuse, on the bed of a reverberatory furnace. The purer tin, being more fusible, gradually melts out, leaving an alloy which has a higher fusing-point ; this, when remelted, forms the inferior class called block tin. The purer metal is then put through a further refining process, and the purest portion of all becomes so brittle that it will split into irregular fragments, known as grain or dropped tin. This condition of tin is a guarantee of purity. Tin fuses at 442*; its specific gravity is 7'29. Tin is a white metal, with a high metallic lustre like silver. It has a yellowish tint, has a peculiar taste and odour when rubbed or held in a warm hand, is very soft and malleable, but of low tensile strength; at 212** is ductile, and may be drawn into wires. If a bar be bent it emits a crackling sound, and becomes hot at point of flexure if bent several times back and forward. If a little lead be added to the tin, the crackle or tin cry will not occur ; it is therefore a rough test of purity. Zinc, till lately chiefly seen in London in the frightful forms with which frantic chimney doctors make the London sky-line hideous, is a metal likely to be more frequently met with by plumbers than was formerly the case, owing to great improvements in its manufacture. It is suitable for roof-work, owing to its qualities of light- ness and durability, combined with the universal latter-day cheapness, a quality to which plumbers also must perforce take heed. Ingot zinc is also known on the market as spelter. It is produced from calamine, or carbonate of zinc, so called from its peculiarity of adhering after fusion in the form of reeds to the base of the furnace ; from blende, or sulphide of zinc, or black jack, as the miners call it ; and from red zinc ore, or the oxide of zinc. These ores are found in England, America, Silesia, Belgium, Sweden, and Spain; they are crushed between rollers and roasted in furnaces by methods differing in each country. Calamine is more easily smelted than blende. Blende requires great care and much time in order to extract all traces of galena, usually mixed with blende, as the presence of lead is not only found to destroy the crucibles used in the reduction of the metal, but also renders the zinc too brittle to roll into sheets. In England the roasted ore is mixed with half its weight of powdered coke or charcoal in crucibles of special construction, covered and placed in circular furnaces, three on each side of fire-bars, and the molten zinc is received in iron vessels placed underneath discharging tubes leading from the crucibles. This metal is remelted, and when the oxide scum is removed it is cast into ingots. When required for rolling into sheets these ingots are again melted at a low temperature and cast into plates of suitable form, which are passed through the rolls at a temperature of 220”. Zinc, or spelter, is a hard, bluish-white metal. At temperatures of 60” to 100” it is brittle, showing a crystalline fracture if broken ; but at temperatures from 212” to 300” it becomes very malleable and ductile, easily wrought. Curiously, at 410’ it again becomes brittle enough to pulverize; and at 793’ zinc fuses. Its specific gravity is 6-86’. Zinc tarnishes rapidly on exposure to moist air; a film of oxide forms on the surface, but this corrosion prevents further corrosion and protects the metal from decay. Near the sea, and in cities where the air contains acids, zinc is seriously attacked. Soot also is injurious in its effects when lying in contact with zinc. These points should be remembered. Sheet zinc of good quality is of uniform colour, and tough enough to admit of frequent bending without splitting. If sheet zinc is dark or blotchy it is of inferior quality, and should be rejected. Zinc expands and contracts under changes of temperature more than either lead or copper ; free play must, therefore, be provided for it in roof-work. It should not be laid in contact with iron, copper, or lead, as voltaic action may rapidly destroy it when moisture is present. Zinc sheets are also liable to bum fiercely if they reach a red heat, and in event of a fire occurring a zinc roof will add fuel to the flames. Zinc is rolled in sheets eight feet or seven feet long, and three feet wide; it can be rolled any length up to twelve feet. The thicknesses recommended for roof -work are known on the zinc-gauge (by which gauge they should be specified) as Nos. 15 and 16, corresponding with Nos. 19 and 20 on Birmingham wire-gauge. The soldering of zinc on roofs should be avoided. Special flashings and end pieces for roof rolls are supplied, and special slips and fasteners to render the use of solder un- necessary, and give freedom for contraction and expansion. Copper, a metal known to the ancients, appears to have been wrought in Cyprus by the Greeks, and hence its name. Copper is sometimes found, in its native state, crystallized in cubes, but usually it is in combination with sulphur, oxygen, and arsenic. The commercial copper is almost exclusively derived from the sulphurets. The most common ore of copper is the copper pyrites, but there are several ores of copper. They are found in Corn- wall, Chili, Cuba, Spain, Australia, America, Saxony. The well-known yellow copper ore is a combination of sulphuret of copper with sulphuret of iron. Copper is remarkably malleable and ductile; it may be beaten into thin sheets or drawn out into fine wire. In tenacity it is inferior only to iron amongst the metals. It has a peculiar taste, and under friction emits an unpleasant odour. Its density varies from 878 for cast copper to 896 for rolled copper. Daniell has placed the melting-point at 1,996* F., when it attains a strong red heat. Pouillet gives 2,050** as the fusing-point. At a white heat it vaporizes. 464 DOMESTIC SANITARY DRAINAGE AND PLUMBING. Copper does not oxidize in dry air at ordinary temperatures. Acids act strongly on copper. Verdigris is a subacetate of copper. It forms rapidly when copper is in contact with cloths dipped in vinegar. Dilute sulphuric and muriatic acids act little on copper, but dilute nitric acid dissolves it quickly. Blue vitriol, or sulphate, is one of the most important salts of copper. Green vitriol, or copperas, is a protosulphate of iron« Swansea, in Wales, is the great centre for the smelting of copper. The metal is hard, tenacious, ductile, and malleable. Copper is one of the best conductors of heat and electricity. It oxidizes slowly in moist air, becoming covered with a verdigris film, forming a protective coating over the metal. Exposure to dry air or pure water has no special effect on copper; but sea-water, and water with chlorides in solution, and spring and river water attack it in many cases, so that it is not always safe to employ copper pipes unless tinned inside, to convey water for culinary purposes. Nor is it a safe metal to use for soil-pipes or in sanitary appliances, the copper pans of pan closets corroding rapidly. Copper is used in good -work for covering flats and gutters. Sheet copper is rolled usually in sizes 4 feet x 2 feet and 4 feet X 3 ft. 6 in. 12, 16, and 20 ounces to the foot, corresponding with Nos. 26, 24, and 22 Birmingham wire-gauge, are the sizes usually specified for roofs and gutters. Plumbers should devote attention to working copper pipes, bending, screwing, and fitting, as they are now being much used for hot-water supply, and are displacing lead pipes. Having thus briefly referred to the metals which the plumber is chiefly concerned with as materials for work, we may just glance at the alloys or mixtures of the metals. PLUMBERS' MATERIALS, 465 These mixtures sometimes exhibit properties so different from those of the metals composing them, that the alloy may be regarded as a new metal. For instance, copper and tin are malleable separately, but an alloy of two parts of copper and one of tin, known as speculum metal, is so hard that it cannot be cut with steel chisels, and is as brittle as glass, and its tensile strength is only one-fifth that of tin, and one-fiftieth that of copper. Again, an alloy of nine parts of copper and one of tin, known as gun-metal, is harder than copper, and its hardness is increased by adding more soft tin. It is more fusible than copper, but cannot be rolled or drawn out. In making alloys it is best to melt the least fusible metal first, adding the others, and keeping them stirred if of different specific gravity. Hard solders, soft solders, pewter, bell-metal, type-metal, gun-metal, brass, bronze, are all alloys. Hard solders can only be used with metals which will endure the heat at which hard solders fuse. For soldering brass-work the alloy is made of one part of zinc spelter to one of copper ; for soldering iron and copper it is made of two parts of zinc spelter to three of copper. These solders are usually granulated by pouring, when melted, through a bundle of twigs into water. For soldering silver, hard solder is made of one part of copper to two, three, or four of silver — generally used for very fine joints in iron, steel, brass, or gun-metal, as well as for silver and light-coloured metals. Soft solders, which melt at low temperatures, are alloyed in various proportions for the use of plumbers and tin- workers, as already described. Plumbers' solder, of such good quality as to be fit for stamping by the Plumbers' Company, is made in proportions of two parts of lead to one of tin; if any variation be made, let it be a small extra percentage of tin, as in working the solder picks up lead from the lead on which it is used, decreasing its fusibility. The solder pot should be capable of holding two hundredweight of metal. Into this put first your lead, as pure as you can get it — pig lead if you want specially good solder, though when making solder it may be well to use up your old scrap lead. When your lead is well melted, stir it and remove the scum, then add half the weight of purest ingot tin, and when it has nearly melted you can assist fusion by adding a little resin. Keep it quietly stirred till hot enough to ignite paper, or make wood smoke quickly when plunged in it, and then cast it in any convenient form of mould you may desire. This will be better solder than the quality usually purchased from lead merchants. By heating the solder more than usual a bloom is thrown up by the tin oxidizing, but this is not desirable. When you pour out solder and let it cool, spots should appear on the top about an inch apart ; if the spots are very close the tin is probably too abundant in the alloy. Old solder joints may be cut off old lead pipes and melted up again, when the workman is experienced in making solder. It saves tin ; but when the time expended in cutting
Key Takeaways
- Rolled lead and zinc sheets are preferred over cast ones for plumbing applications.
- Lead pipes can be made from scrap or antimonial lead, but should not be used for water distribution.
- Tin and copper alloys have specific uses in plumbing based on their properties.
Practical Tips
- Use rolled sheet metals like lead and zinc for more consistent quality in your plumbing projects.
- Consider the environmental factors when choosing between materials like copper and tin-lined lead pipes.
- Understand the composition of solder to ensure it can withstand the temperatures required for your work.
Warnings & Risks
- Avoid using tin-lined lead pipes as they may cause chemical reactions with water, posing health risks.
- Be cautious when working with zinc due to its tendency to burn and add fuel to fires.
- Do not use copper pipes for water conveyance without tinning them inside.
Modern Application
While the techniques described in this chapter are historical, they provide valuable insights into material selection and quality control. Modern plumbers can still benefit from understanding these principles when choosing between materials like lead, zinc, and copper. The use of alloys and proper soldering techniques remains crucial for ensuring the longevity and safety of plumbing systems.
Frequently Asked Questions
Q: How is lead sheet produced?
Lead sheets are produced by casting lead into plates, then rolling them through a series of rollers under pressure to achieve the desired thickness. The process can produce sheets up to four hundred feet long.
Q: What is the difference between rolled and cast lead sheets?
Rolled lead sheets are preferred for plumbing applications due to their uniformity and fewer flaws compared to cast sheets, which may be irregular or contain air holes.
Q: Why should tin-lined lead pipes not be used for water distribution?
Tin-lined lead pipes can produce an alloy that reacts more strongly with water than pure lead pipes, potentially causing health risks and chemical imbalances in the water supply.