The measurements on the piping sketch, Fig. 81, are taken from the accompanying sketch of a dwelling, and if they were to be actually put in, they would fit. The reader would do well to copy this sketch and follow the piping and check the measurements according to the plan, and note how the different risers, drops, etc., are drawn. It is not necessary in a sketch of this kind to draw to a scale. After the different measurements are the letters C.C., E.C., E.E., C.B. and E.B., meaning center to center, end to center, end to end, center to back, and end to back, respectively. Offsetting pipe is a very convenient way of getting the pipe or fittings back to the wall for support. To offset pipe properly and with little trouble, take a piece of scantling 2 by 4 and brace it between the floor and ceiling. Bore a few different-sized holes through it and you will have a very handy device for offsetting pipe. There is a little trick in offsetting pipe that one will have to practice to obtain. The pipe must be held firmly in the place where the pipe is to be bent. Large offsets and bends should not be made; 2 to 4 inches is as large as should be used. Larger offsets that are required should be made with fittings. Always make the offsets true and have the ends perfectly straight. Before putting a piece of pipe permanently in place, always look or blow through it, to ascertain if its bore is obstructed or not. Sometimes dirt or slag will collect and cause stoppage.

Fig. 81.  Pipe sketch. Fig. 81. - Pipe sketch.

Reading The Pipe Sketch

Vertical lines represent vertical pipes (see Fig. 81). Horizontal lines represent horizontal pipes running parallel to the front. Diagonal lines represent horizontal pipes running from back to front. Any line that is drawn perpendicular to any other line stands for a horizontal pipe. A diagonal line separating a vertical line or horizontal line or set of lines represents a different horizontal plane. With this explanation the sketch will be made clear to one after drawing it. The reader should now take each measurement and check it on the plan. This is easily done by using a scale rule. The height of the ceiling is 81⁄2 feet on the first floor, the second floor is 8 feet. The first floor joists are 10 inches, the second floor joists are 9 inches. An outlet is indicated by a small circle. In the piping sketch, this circle is connected with the riser or drop by a horizontal line. At the junction of these two lines a short perpendicular line is drawn, and indicates the direction of the outlet.

Let me again emphasize the need to understand thoroughly this piping sketch, and to become so familiar with it that it can readily be put to use. The value of a mechanic is determined by the quality and the quantity of work that he can turn out; and a mechanic who can lay out his work and see it completed before he starts, and then proceeds to install his work, is by far of more value to his employer than the man who can see only far enough ahead to cut out two or three measurements and spends most of his time walking between the vise and place of installing the pipe.


The system of gas piping must be tested before the pipes have been covered by the advance of building operations. If the job is of considerable size, the job can be tested in sections, and if found tight the sections can be covered. The necessity of having the piping rigidily secured can be appropriately explained here. If the test has been made and the system found tight and some pipe that is not securely anchored is accidentally or otherwise pushed out of place and bent by some of the mechanics working about the building, a leak may be caused and yet not discovered until the final test is made after the plastering is finished. The expense and trouble thus caused is considerable and could have been avoided by simply putting in the proper supports for the pipe.

To test the piping, an air pump and a gage connected with the pipes are placed in a convenient position. The job should now be thoroughly gone over, making sure that all plugs and caps are on and that no outlet is open, also that all pipe that is to be put in has been installed. After this has been attended to, the pump is operated until 10 pounds is registered on the gage. The connection leading to the pump and the piping is now shut off. If the gage drops rapidly, there is a bad leak in the system. This leak should be found without difficulty and repaired. If the gage drops slowly, it denotes a very small leak, such as a sand hole or a bad thread. This kind of leak is more troublesome to find. When it has been found, the pipe or fitting causing the leak should be taken out and replaced. If black caps have been used to cap the outlets, the chances are that a sand hole will be found in one of them. Nothing but galvanized fittings should be used. In case the small leak mentioned above cannot be found by going over the pipe once, there are other means of locating the leak. Two of the methods used, I will explain. If the job is small, each fitting is painted with soap suds until the fitting is found that causes the leak. If the leak is not in the fittings, then the pipe can be gone over in the same way. As soon as the soap suds strikes the leak, a large bubble is made and the leak discovered. It is possible that there are more leaks, so the gage is noted and if it still drops, the search should be continued. The pump should be operated to keep the pressure up to 10 pounds while the search is being made for the leak. When the gage stands at 10 pounds without dropping, the job is then tight. The pump and gage fitting should be gone over first to ascertain if they leak. The other method employed to discover leaks is to force a little ether or oil of peppermint (not essence) into the system by means of the pump. A leak can readily be noted by the odor. To make this method successful, the ether or peppermint should not be handled by the men who are to hunt for the leak. The bottle containing the fluid should not be opened in the building except to pour some into the piping, otherwise the odor will get into the building and as the odor comes out of the leak it will not be noted. For the benefit of the gas fitter, the piping should be tested again after the plastering is completed. The next test is made when the fixtures are put on, and as the piping is tight any leak that develops in this test indicates that the fixtures leak. There are in common use various methods to stop leaks in gas pipe when they are found. If a piece of piping or a fitting is defective, it should be taken out and replaced. This should be remembered so that while the piping is being installed any defects should be noted and the defective fitting or pipe thrown out. Before the gas job is accepted, the gas company will inspect it and look for traps and sags in the pipe. Therefore, the piping should be installed without any traps and it should be arranged to pitch toward the meter, or toward a convenient place from which any condensation can be taken out. If provision is not made for this condensation, it will accumulate and stop the flow of gas.