fra0105
plumbing01.htm Essentials of Plumbing

Unit I: Legends,

MEASURING PIPE RUN LENGTHS

1.   A plumber is often required to make a list of plumbing materials from a construction drawing or a set of construction drawings. The list must contain all the materials by type, size, and length to install a part of or the complete plumbing system.

2.   Horizontal pipe run lengths are measured using either graphic or ratio construction scales.

a.   To make graphic scale measurements with a divider, first spread the divider from the center of one fitting to the center of the next fitting to get the length of the pipe run (fig 2-1). Then place one end of the divider on 0 (fig 2-2). Where the other end falls on the scale is the pipe run length.

FIGURE 2-1.   DIVIDER ON DIAGRAM

FIGURE 2-2.   DIVIDER ON SCALE

b.   To make graphic scale measurements with the straightedge of a piece of paper, place the straightedge along the pipe run and mark the center of each fitting (fig 2-3) on the paper. Then place one mark on 0 (fig 2-4). Where the other mark falls on the scale is the pipe run length.

FIGURE 2-3.   STRAIGHTEDGE ON DIAGRAM

FIGURE 2-4.   STRAIGHTEDGE ON SCALE

c.   To make ratio scale measurements with a ruler, place the zero of the ruler at the center of one fitting and the measuring edge along the pipe run. Read the ruler mark at the center of the other fitting. See figure 2-5. If the ratio scale is 1/4 inch = 1 foot, the reading of 1 5/8 inches on the diagram means 6 feet 6 inches of pipe.

FIGURE 2-5.   USE OF RULER WITH RATIO SCALE

3.   Vertical water-pipe lengths are computed using simple math. The pipe run can come down from the ceiling level or up from below the floor level.

a.   To determine a pipe run length from the ceiling level, use the floor-to-ceiling measurement, the distance the pipe hangs from the ceiling, and the fixture's rough-in measurements. To find the length of pipe X in figure 2-6, make the following computation:

Floor to ceilings -- 7 feet 11 inches.
Pipe hangs from ceiling -- 0 feet 2 inches.
Fixture rough-in measurement -- 4 feet 6 inches.
7 feet 11 inches minus 0 feet 2 inches = 7 feet 9 inches.
7 feet 9 inches minus 4 feet 6 inches = 3 feet
3 inches.

The length of pipe X is 3 feet 3 inches

FIGURE 2-6.   PIPE RUN FROM CEILING

b.   To find a pipe run length from below floor level to ceiling, use the floor-to-ceiling measurement, the distance the pipe hangs from the ceiling, and the distance the pipe is below the floor. To find the length of pipe Z in figure 2-7, make the following computation:

Floor to ceiling -- 7 feet 11 inches.
Pipe hang from ceiling -- 0 feet 2 inches.
Pipe below floor -- 0 feet 4 inches.
7 feet 11 inches minus 0 feet 2 inches -- 7 feet 9 inches.
7 feet 9 inches plus 0 feet 4 inches -- 7 feet
13 inches or 8 feet 1 inch.

The length of pipe Z is 8 feet 1 inch:

FIGURE 2-7.   PIPE RUN FROM BELOW FLOOR TO CEILING

c.   To find a pipe run length from below floor level to a fixture, use the distance the pipe hangs below the floor and the fixture's rough-in measurements. To find the length of pipe Y in figure 2-8, make the following computation:

Pipe hangs from floor -- 3 inches.
Fixture rough-in measurement -- 11 inches.
11 inches plus 3 inches = 14 inches.

The length of pipe Y is 14 inches.

FIGURE 2-8.   PIPE RUN FROM BELOW FLOOR TO FIXTURE

1.   Use the graphic scale given in figure 2-9. What is the length, in feet, of line X?

FIGURE 2-9.   USE OF GRAPHIC SCALE

Did you get 7 1/2 feet? If not, read Lesson 1, paragraph lb, again. If you did get 7 1/2 feet, good work. Continue with the lesson.

2.   Use the ratio scale in figure 2-10. What is the length, in feet, of line Z?

FIGURE 2-10.   USE OF GRAPHIC SCALE

Did you get 8 feet? If you did, good work. Continue with the lesson. If not, read Lesson 1, paragraph lb, again until you understand ratio scales.

3.   Refer to figure 2-11. Compute the length of pipe Z.

FIGURE 2-11.   MEASUREMENT OF PIPE

How did you do? Did you get 3 feet 8 inches for the length of pipe Z? Let's see how we got this answer.

Floor to ceiling -- 8 feet 0 inches.
Pipe hangs from ceiling -- 4 inches.
Fixture rough-in measurement -- 4 feet 0 inches.
8 feet 0 inches minus 4 inches = 7 feet 8 inches.
7 feet 8 inches minus 4 feet 0 inches = 3 feet
8 inches.

Therefore, the length of pipe Z is 3 feet 8 inches. If you have any problems with this computation, study the example closely. Get your squad leader or platoon sergeant to assist you if you need additional help. Then continue with the lesson.

4.   Vertical waste-system-pipe lengths are computed in the same way as vertical water pipe.

a.   To find a waste-pipe-run length from below the floor level to a fixture, use the distance from the center of the bend to the floor and the fixture's rough-in measurements. To find the length of pipe needed in figure 2-12, make the following computation:

Bend to floor -- 6 inches.
Rough-in measurement -- 17 inches.
6 inches plus 17 inches = 23 inches.

The length of pipe required is 23 inches.

FIGURE 2-12.   VERTICAL WASTEPIPE

b.   To find a waste-pipe length from below the floor up through the roof, use the total of all measurements from the bend below the floor to-VTR. To find the length of pipe needed in figure 2-13, make the following computation:

 Bend to floor Floor to ceiling Ceiling to roof Roof to top of VTR Total 8 inches 7 feet 11 inches 2 feet 2 inches 1 foot 0 inches 10 feet 21 inches

The length of waste pipe required is 10 feet 21 inches or 11 feet 9 inches.

FIGURE 2-13.   VERTICAL WASTE PIPE TO VTR

Refer to figure 2-14. Compute the length of the vent through the roof (VTR) shown.

FIGURE 2-14.   VTR MEASUREMENT

Did you get 12 feet 1 inch? Let's see how we arrived at that answer.

If you had any problems with this exercise, look at the drawing again until you understand. Continue with the lesson.