The safe use of white enameled pipe is out of the question with the caulked joint, because the jarring produced by the caulking tool tends to crack the enamel.
The bell or hub and spigot joint, however, is still used everywhere, and is perhaps found in nine-tenths of the plumbing work in buildings today. Its great importance therefore demands further careful and critical examination. The use of the joint should be prohibited by law. In view of all its faults, and its great and undeserved ascendancy over mankind, it might be styled the King of Evil Joints.
This joint is made usually with lead (the "Saturn" of the ancient alchemist, and the "Satan" of the modern plumber) and oakum or jute, A gasket of jute or similar fibre is inserted into the cavity of the bell or hub, and the spigot end of the length next above it is set firmly down upon it, or the gasket is rammed in with a tool after the lengths are set up. The gasket is used to prevent the lead from running out of the joint and obstructing the bore of the pipe at some point below, besides wasting the lead.
The lead is now poured upon the gasket from a ladle, and shrinks as it cools. The caulking tool must then be used to expand it again and drive it into the cavities and pores of the iron. A faithful and skillful operator can, by perseverance, succeed in fitting the lead into the iron at all parts of its circumference, so as to make it light for a time, just as a painstaking dentist can drive the gold, by patient Tabor, into the cavities of a tooth and temporarily arrest its decay. But the process in both cases is slow and uncertain. The dentist confines his caulking to a single small spot, well within his reach, and he labors with extraordinary care. Yet the filling often fails when put to the test, even though the mouth is not as a rule alternately subjected to such severe strains of expansion and contraction produced by alternating heat and cold as in the iron piping.
The plumber must work quickly over an extended field, often in awkward positions. He must perforin a very delicate task with very clumsy tools. The metals to be welded together are often so placed that it is impossible, without the utmost skill and patience, to reach them properly. The result is that when put to the test the joint almost always fails. The presence of the lead prevents the formation of a good rust joint. Extra heavy pipe and hubs are required to withstand the blows of the caulking tool. Lighter pipes cannot be made tight without danger of cracking the iron. I have made a number of tests on pipes of different thicknesses with the aid of an experienced pipe layer and caulker. With double thick pipe, joints could be made which would stand the hydraulic test or a water pressure equal to that produced by such a test at the bottom of an average city house. Almost invariably a second caulking was found necessary after the plumber had carefully done the work once in a manner which he considered sufficient, and had pronounced it completed. The single thick pipe could not be made to stand the water pressure test at all. It was cracked by the caulking iron before it had been made tight. Were the hydraulic test made, now often recommended to be applied to all the cast iron soil pipes set up within the last year in city houses, not one in a hundred would hold water. The experiments of Col. Waring and other authorities in this direction fully corroborate this statement.. Col. Waring says: "I have recently had occasion to test the soil pipes of a large house of the best class, where the greatest effort was made to secure tight work, where the joints were so exposed that there was no difficulty in caulking them thoroughly, and where there was every reason to suppose that every joint was absolutely tight. On closing the outlets and filling the pipes with water the whole system leaked like a sieve."
It is now generally acknowledged that a plumber's caulked joint is rarely either air or water tight, though a vast amount of lead and labor is spent on them to make them so. When we reflect that the sole aim and object of a soil pipe joint is to make a gas and water tight connection between pipes, we see that the method commonly employed is an absurdity and reflects little credit upon human ingenuity.
Now the very persons who are loudest in their defense of cast iron hub and spigot piping, in spite of the acknowledged impossibility of making with it a single permanently tight joint throughout the entire building, are yet the most strenuous advocates of the costly special trap vent law.
They accept the certainty of a hundred openings in the soil and drain pipe system, and yet subject the house owner to tremendous expense in applying an absolutely ineffective watch over a few trap seals, seals which with proper traps could not possibly be destroyed, even without the vent.
The inconsistency is sufficiently glaring.
Expansion and contraction in the iron piping caused by hot water or steam soon widens the original openings between the lead and iron in the joints. The expansion of the spigot is in such cases greater than that of the hub because it is on the inside nearest the heat and comes directly in contact with it, while the hub is protected both by the spigot and the caulking. Hence the lead is temporarily compressed between the spigot and the hub, and, being inelastic, does not resume its original bulk when the pipes cool again. A minute opening is thus formed round the spigot, and the joint leaks. The opening may be very small, even microscopic, but it is sufficient to permit the still smaller particles of soil pipe air to freely pass, and when we reflect that the opening extends entirely round the pipe and is repeated at every joint in the building, the aggregate leakage becomes quite formidable.
The longitudinal expansion and contraction of the soil pipe also affects, often still more seriously, the caulked joint. When a length of pipe contracts the spigot is drawn away from the hub of the adjoining pipe, and if the second pipe is held fast, the hub cannot follow it. The two must, therefore, separate slightly, and the movement draws the lead ring outwards with it. The spigot then returns again under the influence of expansion, but the lead ring does not necessarily return with it, but often remains protruding slightly from the socket, and the joint leaks. This process may be repeated until the lead has been drawn out a considerable distance from its proper position. Every plumber knows how common a thing it is to find the lead thus protruding from the socket in the pipes which have been for a certain time in use in trying positions.
The caulked joint is incapable of resisting any severe tensile strain which is often brought to bear upon it by the weight of any member of construction or by the settling of the house. The only thing which offers any resistance to such a strain is the small ring of lead between the two metals. This may be extremely feeble where but a small quantity of lead is used and the caulking has been spared.
Another serious objection to this joint is the difficulty of disjointing pipes in which it has been used for alterations. The usual way to take out a pipe once so put together is to break it to pieces, and then remove it by degrees.
There is, in fact, no practicable alternative; for to melt off the lead would not only be expensive and dangerous, but involve the disjointing of quite a number of lengths of pipe in order to enable a single spigot to be lifted two inches, or enough to disengage it from its hub. Now, alterations in buildings are necessarily so frequent that this objection becomes a serious one.
The necessity of using fire in a house in process of construction for melting the lead necessary to make this joint is also a formidable objection to it, on account of the danger of igniting the surrounding carpenters' litter and burning down the house.
No melted lead is required today in plumbing, brass screw jointed pipe being preferable.
Still another very serious objection is the temptation this joint opens for fraud. The lead may be partially or even wholly omitted without very great risk of detection, since it is out of sight, and frequently immediately covered by a coat of paint. The caulking may be still more easily slighted. If the hydraulic test is not demanded by the architect, a coat of paint or a little putty will easily make the joint stand the smoke or peppermint test. A few of the joints well within the reach of the house owner may be filled with genuine lead, while all those which are covered by floor boards, or are not easily accessible, may be composed of paper and sand and covered with putty. Possibly a thin coating of lead may be poured on top to present an honest appearance, and satisfy the suspicious and shrewd house owner who goes about probing the nearest joints with his penknife in order to ensnare the "rascally plumber."
The "Sanitary Engineer" narrates a striking illustration of audacious fraud in the use of paper and sand joints, as follows "I cannot better describe it than to quote a conversation I recently had with a journeyman plumber who had been looking for employment. He said: 'I was looking for work, and went into a shop on Second or Third street - I am not sure which - and asked for a job. I was told that they needed no more help, and the clerk proceeded to inform me that they had a man who was able to iron-pipe two ordinary three-story and basement houses in a day. I pretended to doubt this statement, when he said, "Why - bet the boss five dollars he could do it, and he did it and won the five dollars." I asked the man, who was standing by, how it was possible to even stick the lengths together, or even caulk them at all. He replied, "Oh, I just put a little paper in each joint, poured in some sand, and then when the pipe was all up, I went over the job with my pot and ladle and poured a little lead on the front of each hub." ' This frank admission fairly indicates the character of a great deal of work that has been done this summer in many parts of the city."