218. The location of gas fixtures is generally indicated by a star, thus *, and the number of burners on each fixture, together with the height of the fixture above the floor, is usually stated in the specifications.

To facilitate the work of running the pipes and of estimating their proper sizes, plans should be made of the piping on each floor. On these should be noted the position of each fixture, its height from the floor, and the number of burners required for each.

The number of burners and the kind of fixture may be conveniently indicated by the symbols shown in Fig. 78. A, B, and C represent side lights or brackets having 1, 2, and 3 lights, respectively, each large dot representing a burner. In a similar manner, D, E, F, G, H, and I represent drop lights having 1, 2, 3, 4, 5, and 6 burners, respectively. The manner of using these symbols is exemplified by the plans, Figs. 80 and 81.

Fig. 78.

219. The horizontal piping should be indicated by plain black lines, and each floor plan should show only those pipes which are to be actually run in the floor of that story, or upon the under side of it.

The points at which risers or drop pipes are to be connected to the horizontal pipes should be indicated as shown in Fig. 79. Thus, an X at j indicates that a drop pipe descends from that point, and a O at k indicates that a riser ascends from that point. The symbols O and X combined as at l, indicate that the vertical pipe extends both above and below. At m is indicated a drop pipe leading to a bracket or side light having two burners.

Fig. 79.

If the lineal measurements are to be embraced in the plans, the length of each pipe should be figured from center to center of fittings, and the diameter should be written close to the figures indicating the length. Thus, the pipe between l and k is shown to be 1 1/4 inches in diameter and 6 feet 3 inches between centers of fittings.

The length of each riser or drop pipe should similarly be indicated by figures placed near the symbol, and connected to it by a light line; thus, at j we have a drop pipe 1/2 inch in diameter, descending 4 feet 6 inches to center of fitting; at k we have a riser 3/4 inch in diameter, ascending 8 feet 2 inches; at l we have a riser 1 1/4 inches in diameter, ascending 3 feet 4 inches, and a drop pipe 1 inch in diameter, descending 8 feet 2 inches.

In order to show which figures belong to the drop pipe at l, it is necessary to place an X before them, as shown. Where figures are crowded, it is advisable to draw a O around the figures indicating diameters of pipes, in order to clearly distinguish them from all others

Fig. 81.

If any of the vertical pipes require to be offset or bent to pass around obstructions, etc., or a horizontal pipe requires to be run along a wall at a height between the floor and the ceiling, a reference letter should be placed conspicuously at that point, and a corresponding note made upon the margin of the drawing. A diagram of the special pipe required should be made and attached to the drawing.

Gas-fitters' plans are sometimes made in perspective; but if the work is at all complicated, the drawing is likely to be very confusing, especially if the draftsman is a little unskilful.

The plan recommended above has the advantage that several sets of piping for various purposes may be indicated upon the same drawing. Thus, pipes for gas, steam, and water, and tubing for electric wires, may be shown by using differently colored inks for the various systems of pipe.

220. Fig. 80 shows the first-floor plan of a common two-story and basement dwelling house. The second-story plan is shown in Fig. 81. These figures are supposed to represent tracings from the general drawings with the gas piping drawn in.

The meter a is placed in the basement, and all the piping shown on this plan is run along or under the basement ceiling, except b, which is a 3/8-inch horizontal branch to supply the lavatory bracket from a 3/8-inch riser c, run from the basement to the brackets on the stair landing above. A distributing main d runs directly from the meter outlet to the riser e, and all the branches which supply gas to the brackets of the first floor, also the basement lights, are taken from this pipe.

The chandeliers or pendants which illumine this floor are supplied with gas from the pipes shown in Fig. 81. These pipes run under the floors and across or between the joists. They also supply all brackets which illumine the second floor.

The pipes are proportioned to give an abundant supply of gas to the entire building when all the jets are burning at the same time. They are also all laid to pitch back towards the meter, where a drip cup may be placed. The piping in Fig. 81 is so arranged that no floor joists will be cut at a greater distance than 2 feet from a point of support. The joists all run from front to rear of the building.

There are many other ways of running the pipes for this work, but the drawings show a method probably as good as any.

221. In selecting the location of the pipes, the architect should be governed by the following considerations:

1. The pipes should run to the fixtures in the most direct manner practicable.

2. The pipes must be graded to secure proper drainage without excessive cutting of floorbeams, or otherwise damaging the building.

3. Pipes which run across the floorbeams should be laid not more than one foot away from the wall, so as to avoid serious injury to the floor by the cutting of beams near the middle of their span.

4. Fixtures should be supplied by risers, rather than by drop pipes, as far as practicable.

5. All pipes should be located where they are accessible for repairs with the least possible damage to the floors or walls.

222. Service-pipe connections should be made to the top of the street main. The pipe should be inclined so that it will drain into the main, but if this is not possible, it should be inclined toward the building, and should be provided with a suitable drip cup, from which water may be conveniently drawn off.

A shut-off cock should be placed in every service pipe at the curb, and this should be enclosed in a suitable box extending upwards to the surface of the pavement, and closed against the entrance of dirt, water, or snow by a tight cover.

223. Meter connections to service pipes, and also to the house pipes, should be made with lead pipe so that they will bend and relieve the couplings on the meter from injurious strains. The meters are usually furnished and set in place by the gas company.

224. Gas pipes should not be exposed to the weather, if possible to avoid it, and care must be taken to protect them from freezing winds, or air-currents. The moisture will condense upon the interior of the pipe and form ice, and the deposit will increase in thickness until the pipe becomes choked. Exposed pipes should be covered with hair felt or other good non-conducting material, which should be made thoroughly waterproof by a covering of painted canvas. Good protection is especially necessary if the pipe contains carbureted air or gasoline gas.

Iron gas pipes should not be allowed to touch lead pipes or electric wires which run across or near them, because the continual shifting caused by changes in temperature will ultimately wear a groove or thin spot in the softer pipe, and the insulation of the electric wire will be cut through, thus making a ground or short circuit.

If a metal pipe runs within two inches of an electric wire, they should be separated by a non-conductor of some description. For example, the pipe may be wrapped with four or five layers of rubber tape.