plug, capable of holding very heavy pressures is illustrated in Fig. 86.

The single testing plug of Fig. 84 operates by the expansion, against the sides of the pipe, of a heavy rubber ring, which is ex

panded by being compressed between an iron plate and a wing nut working on a screw. The operation of the double testing plug is as follows: The hollow piece F connects the plug D and the plug B

rigidly, and inside of it the rod G works. When the wheel A is turned against the nut E, it expands the plug B, and the plug D is

expanded without disturbing the other plug, by turning up the nut C.

Figs. 87 and 88 show methods used in giving the smoke test. For the stopping of openings, ordinary testing plugs may be used. In admitting smoke to the system, however, the method shown

FIG. 88.-Plumbing under Smoke Test.

in Fig. 88 is generally used. Smoke-testing plugs which admit smoke through them, such as in Fig. 87, are also very handy for this purpose.

In "Modern Plumbing Illustrated," by the author of this work, the subjects of water, air, peppermint and smoke tests are taken up very comprehensively, in all their details, in connection with both large and small work.

*"Modern Plumbing Illustrated" by R. M. Starbuck is published by The Norman W. Henley Publishing Co., 132 Nassau Street, New York. Price $4.00.

CHAPTER XI

SOIL PIPING ROUGHING-IN

THE term soil pipe is used in a popular manner to designate all iron drainage piping, and it is also applied to the cast-iron piping used on the vent system. As a matter of fact, soil pipe is that part of the iron pipe of the drainage system through which the waste from water-closets flows. Other pipe, even though of the same size as the soil pipe, but carrying waste from other fixtures, is called waste pipe. However, the term soil pipe has come to be used so universally to designate all cast-iron pipe, whether used as soil, waste, or vent, that it will be more convenient to refer to it occasionally in this general way.

In Fig. 89 is shown a system of soil piping to which reference will be made later. In this system the main back-air or vent pipes are of cast iron. Wrought iron is being used very largely for this purpose at the present time, and it appears to be replacing the cast iron on this part of the system, in many sections.

In fact the use of wrought-iron pipe for vent work has become almost universal. Long, straight lines of wrought-iron pipe are more quickly run than cast iron, and closer connections can be made.

Several matters which might properly be considered here have already been taken up, such as the supporting of horizontal soil piping, etc. Vertical lines of soil and waste pipe should be supported at each floor by a clamp placed under the hub of a pipe or fitting, and firmly screwed to the timber. This support not only prevents the settling of the stack, but also prevents any side motion of the pipe.

All first-class plumbing ordinances now require the use of extra heavy cast-iron pipe on the drainage system in preference to standard pipe. The reason for this is that the standard pipe being much lighter has more sand holes and defects than the extra heavy.

Unless the standard pipe is cast perfectly, one part of the circumference will be very thin, while the section directly opposite will be correspondingly thick. When in this condition it takes only a slight blow to break the pipe. In the cutting of standard pipe and in the calking of joints, split lengths of pipe and split fittings are much more liable to result than in the use of extra heavy pipe. Many times such defective pipe and fittings are not cast aside as they should be, but made use of, the defects being patched up with tar so that they may not be detected. Principally to make such practices impossible, some ordinances demand the use of soil pipe which has no asphaltum coating.

The weights of different materials used on the plumbing system are, viz.:

Weights of Cast-Iron Pipe

2-inch Standard C.-I. Pipe Weighs 3 lbs. per foot

As will be seen later, in the description of the Durham plumbing system, whenever wrought-iron pipe is used for drainage purposes, the fittings used in connection with it should be of cast iron. They should be of the style known as extra heavy cast iron, recessed, and threaded drainage fittings. These fittings should also be used on main vent lines of wrought iron, although it is true that in many cases they are not used on such work.