pipe on the plan. Other line symbols identify the
have smaller inside diameters because their wall
proposed use of the pipes. The size of the required
thickness is greater. Piping over 12 in. in diameter
piping should also be noted alongside each route
is referred to by its outside diameter (O.D.).
of the plan. Piping up to 12 in. in diameter is
referred to by its nominal size, which is
approximately equal to the inside diameter (I.D.).
The exact inside diameter depends on the
The pipe-fitting symbols shown in figure 8-29
classification of the pipe. Heavy types of piping
are the basic line symbols used for pipes, in
Figure 8-29.-Pipe-fitting symbols.