In construction drafting, a mechanical (or utility) plan normally includes both water distribution and sanitary drainage systems combined, especially on smaller buildings or houses. The plumbing layout is usually drawn into a copy of the floor plan for proper orientation with existing plumbing fixtures, walls and partition outlines, and other utility features. Figure 8-27 shows a typical plumbing layout. The reproduction is, unfortunately, too small to be easily studied, but you can see that it uses the mechanical symbols.

Figure 8-27.  Typical plumbing layout for a small residential building.

Refer to ANSI Y32.4-1977, Graphic Symbols Used in Architectural and Building Construction and MIL- STD-17-1,  

As shown in figure 8-27, the cold-water service line, which enters the building near the laundry trays, is indicated by a broken dash-and-single- dot line, while the waste pipes are indicated by solid lines. If you follow the cold-water service line, you will see how it passes, first, a 1-in. main shutoff valve below the floor and just inside the building wall. From here, it proceeds to a long pipe running parallel to the building wall and hung under the floor joists, which services, beginning at the right-hand end, the cold-water spigot in the sink, the cold-water spigot in the laundry, the hot-water heater, the boiler for the house heating system, the flushing system in the water closet (W.C.), the cold-water spigot in the bathroom washbasin, and the cold-water spigot in the bathtub. The below-the-floor line is connected to the spigots by vertical RISERS. Valves at the hot-water heater and boilers are indicated by appropriate symbols. From the hot-water heater, you can trace the hot-water line (broken dash-and-double-dot line) to the hot-water spigots in the sink, laundry, bathroom washbasin, and bathtub. This line is also hung below the floor joists and connected to the spigots by risers.

You can see the waste line (solid line) for the bathtub, washbasin, and W.C. (with traps indicated by bends) running under the floor from the bathtub by way of the washbasin and W.C. to the 4-in. sanitary sewer. Similarly, you can see the waste line from the laundry running to the same outlet. However, the kitchen sink has its own, separate waste line. The bathroom utilities waste lines vent through a 4-in. pipe running through the roof; the sink waste line vents through a 2-in. pipe running up through the roof.

As stated earlier in this chapter, the Engineering Aid is not expected to design the system, but the main objective is to draw a workable plumbing plan for use by the plumbing crew or any other interested parties. In order to accomplish this, the EA must be familiar with the terms, symbols, definitions, and the basic concepts of the plumbing trade.

As a rule, plumbing plans should show the location of the fixtures and fittings to be installed and the size and the route of the piping. The basic details are left to the plumber (UT), who is responsible for installing a properly connected system according to applicable codes, specifications, and good plumbing and construction practices. Generally, plumbing plans consist of four types of symbols: piping, fittings, valves, and fixtures.