There is no difference in the principles of construction between the Durham system and the plumbing system as ordinarily constructed. The only difference in the Durham system is that it is constructed entirely of wrought-iron threaded pipe and cast-iron fittings.

On the Durham system all joints are made with screw threads, no caulked lead joints being used. The Durham system is shown in Plate 44, with a detail in section, of the style of cast-iron fitting used on Durham. Fittings of other than recessed construction should not be used on any part of the drainage system. On vent work in connection with the Durham drainage system, galvanized, cast, or malleable steam and water fittings of ordinary make may be used. The purpose in using recessed fittings is that the alignment of the inside surface of drainage pipe and fittings may be as even as possible, with no ends of pipes that screw into fittings presenting shoulders against which solid matter flowing in the waste may find lodgment.

Plate XLIV. The Durham System - The Destruction Of Pipes By Electrolysis

Plate 44. The Durham System

The Durham System 113

The use of cast-iron pipe and fittings is free from this trouble, for the hubs are sufficiently recessed to allow an even inside alignment. In the use of common steam and water fittings on cast-iron drainage work, there being no recesses in such fittings, the ends of all pipes entering fittings present shoulders against which lint and other materials in the waste may collect. It may be stated, however, that this trouble is experienced in a greater degree in connection with Durham work than in cast-iron soil piping. For this reason, special care should be taken in cutting wrought-iron pipe for drainage use, and all burs on the ends of such pipes should be reamed out. The weights of wrought-iron pipe for drainage purposes should not be less than the following:

Diameter of Pipe

Weight per Foot

1 1/2 in. . .

..... 2.68 lbs.

2 "."..

..... 3.61 "

2 1/2" . . . .

..... 5.74 "

3 "....

...... 7.54 "

3 1/2

..... 9 "

4

..... 10.66 "

4 1/2 " • • • •

..... 12.34 "

Diameter of Pipe

Weight per Foot

5 m.....

. . . . 14.5 lbs.

6 ".....

.... 18.76 "

7 ".....

. . . . 23.27 "

8 ".....

. ... 28.18 "

9 ".....

• • • • 337 "

10 ".....

. . . . 40.06 "

All fittings used on Durham work and on all vent work should be galvanized. Short nipples, in which the unthreaded part is less than 1 1/2 in. long, should be made of weight and thickness known as "extra heavy" or "extra strong." This provision is to guard against crushing and splitting, which is liable to happen in the use of nipples made of ordinary pipe.

Joints on the Durham system should be made up with red or white lead, applied to the male part of the thread. When thus applied there is less opportunity for the lead to squeeze through into the interior of the pipe and form an obstruction.

Care should be taken that all such obstructions are removed when the joint is made. When wrought-iron or brass pipe is connected into cast-iron pipe, the connection may be made by a caulked lead joint or by a screw joint.

Connections between lead and wrought-iron pipes may be made by means of a brass ferrule caulked or screwed into the cast iron, the lead connection to the ferrule being made by means of a wiped joint.

An advantage claimed for the Durham system by its friends, is that a screw joint, being as strong as the pipe is, there are no weak points in a line of such pipe, whereas it would be folly to claim any such thing as this regarding a line of cast-iron pipe with its caulked joints. This argument is followed by the claim that the above being true as regards a vertical line of wrought-iron pipe, so long as it rests at its base on a firm foundation, there is no necessity for side supports, and that it may be carried thus, through the height of the tallest buildings. This would not seem plausible, for the reason that any line of drainage pipe, whether vertical or horizontal, of cast or wrought iron, should be given lateral support in order that it may be rigid and not subject to any lateral movement. Even though the screw joint is a strong one, lateral motion in a long line of pipe will often result in snapping the pipe at one of the screw joints or in breaking a fitting. Furthermore, if a vertical line of cast-iron drainage pipe be given the support that it should receive, it will not sag or settle so that the caulked joints will be forced out of the hubs, a claim that is made against the use of cast-iron pipe. It is true that in the construction of the plumbing system the proper supporting of heavy piping is not given the attention that it should receive, damage to caulked joints often resulting thereby. It is also true that lines of cast-iron pipe properly provided for, suffer no more from broken joints than wrought-iron lines, and are free from certain serious evils which wrought iron is subject to. The Durham system, which has received its name from the inventor of certain patents on the application of wrought-iron pipes to drainage systems, is now extensively used in high city buildings, mainly because of the advantages thus claimed for the system, and it is a question whether such extensive use would have resulted if the cast-iron system had been properly handled. It has often been placed in high buildings with not much more provision being made for supporting its great weight than is made in the system of a private residence, and it is mainly due to this cause that cast iron has been somewhat superseded in very large work. There are many uses to which iron piping is put, in which the use of wrought iron for drainage purposes is preferable. Greenhouse work is an important instance. In this work, where there is much expansion and contraction due to changes in temperature, the caulked joint will not stand nearly so well as the screw joint. This is also many times true in the case of factory work, where constant and severe vibration tends to start the caulked joints of cast-iron piping.

A very strong argument against the use of the Durham system is the fact that wrought-iron pipe has a much shorter term of life than cast-iron pipe, particularly when buried underground. This fact is testified to very strongly by the demand made by all plumbing ordinances dealing with the subject of the Durham system, that whenever pipes connected with the system are to be run underground, such pipes shall be of cast iron. This feature appears in the illustration in Plate 44. Regarding the life of wrought-iron pipe, it may be stated that under certain unfavorable conditions, plain wrought-iron piping that has been installed not longer than eight to ten years has had to be renewed, owing to its deterioration.