With reference to the action of frost, lead pipe has an advantage in that the diametrical expansion of the water when freezing does not burst the pipe at the point frozen, unless it has been repeatedly swelled from the same cause. Lateral extension of the core of ice in the portion frozen, crowds the water which it cannot compress; and, as the ice is frozen to the wall of the pipe, the weakest place ruptures. Sometimes a faucet ball will be driven in, and occasionally a coupling collar will be stripped of its threads; but usually room is made for the extra volume of the water by the pipe swelling to an egg-shape and bursting at one point. Such a break can be repaired by wiping a single patch or joint on the original pipe.
Frost breaks in lead pipe nearly always occur on the house side of the point frozen, because the water in the street end is easily driven toward the main. Air-chambers on the house service would often obviate the bursting of lead pipe; but where the type of faucets or a limited pressure does not require their use in order to prevent reaction, plumbers frequently omit them, under the impression that air-cham bers can serve no other good purpose.
With iron pipe, frost breaks are more serious. Diametrical expansion splits the pipe at the point frozen every time freez ing occurs; and lateral extension of the ice staves in the faucet stems, etc., quite as frequently as would happen with lead pipe under the same conditions. Of late years, the improvement in types of buildings, more careful provision against frost on the part of plumbers, and the vigilance of the Weather Bureau in giving warning of ap proaching cold snaps, have made insignificant the amount of damage by frost in both kinds of pipe.
Lead pipe, as a rule, requires less trench work on ground lines than iron pipe, because drilling, even if very poorly aligned, will often suffice to get the pipe in place. There are numerous instances, how ever, where longer stretches of iron pipe have been placed in drilled holes than would be practicable with lead at the same excavating cost. It is well to remember that any small line of house service in the ground should be placed deeper, so far as immunity from frost alone is concerned, than is necessary for the protection of large pipes in the same locality, because the volume of contents in house pipes is small, the wall surface of the pipe relatively large, and the flow of the water not so regularly maintained.
The action of natural waters on lead has been a matter of wide discussion by able men. The subject of possible contamination of water supply through the agency of lead conduits, is too broad, how ever, for full consideration here, and will therefore be but briefly touched upon. This trait of lead has been voiced against its use, with more or less effect; but known cases of poisoning from this source have been exceedingly rare. Galvanized-iron pipe charges
the water with salts of zinc when the water contains certain impurities; and most other kinds of pipe are also more or less open to objection at times by reason of their injurious effect on the water, the staining of fixtures, etc. Some of the salts of lead formed by the agency of water conveyed through lead supply pipe, are protective. Others, without doubt—fortunately of rare occurrence is actual practice—are corrosive. Sulphate or phosphate of lime, in solution, will part with its acid in passing through lead pipe, the acid combining with a new base (lead) and forming sulphate or phosphate of lead as the case may be. Chloride, sulphate, nitrate, borate, and other compounds of lead, may be similarly formed. These incrust the pipe; and such of them as are practically insoluble in water protect the lead from further attack, thus preserving the quality of the water. Carbonate, sulphate, and phosphate of lead, which doubtless form most frequently in lead water pipes, belong to the protective class. Of course, not all the compounds mentioned are encountered in any one source of supply. Chemical compounds designed to produce an insoluble incrustation have sometimes been purposely placed in solution, and allowed to stand in systems of lead supply pipe where it was known that the water to be commonly used would otherwise be dangerously corrosive. In view of the possibility of such precautionary measures, the dele terious effect of lead on many water supplies, and the consequent menace to health if lead were used indiscriminately, could hardly alone to any appreciable extent result in the substitution of pipe of other material.
Lead has been thus dwelt upon at the outset, because the industry of plumbing itself derived its name from this metal (Plumbum, Latin for "lead"). A discussion sufficient to define broadly the present and past status of the metal in the plumbing business, is certainly apropos in this connection. To many persons, the term "Plumbing" sug gests lead and lead work generally, without regard to its distinctive forms, some of which are quite foreign to the ordinary trade meaning. To those acquainted with the building practices of Europe, visions of lead-covered roofs and spires, rainwater heads, etc., in addition to manifold other uses of the metal not common in America, may come to view in the mind's eye when "plumbing" is mentioned. To Ameri can plumbers of the past generation, "plumbing" suggested stacks of hand-made lead soil and waste pipe; hand-made lead traps; lead "safe" pans cumbersomely boxed-in under fixtures; ridiculously small lead ventilation pipes; lead drip-trays; lead supply pipes (sometimes also hand-made); all "wiped" joints and seams; and blocks, flanges, braces, boards, and boxes galore, jutting out in pro fusion, for supports, covering, etc.