148 Chapter 6
The first component connected to a fixture is a trap. Traps are located at every fixture. A trap is the
u-shaped pipe found below a sink. Some traps are part of the design of the fixture and are not visible,
as in a toilet or double sink. The trap catches and holds a small quantity of water to provide a seal. This
seal prevents gases from the sewage system entering the building.
From the trap sewage travels through drainage pipes in branch lines to a vertical stack. A soil stack
carries waste from toilets. A waste stack carries the other waste from a sink, washing machine, or dish-
washer. All drainage pipes must be connected to vents. Vents are open to the outside air. Vents allow
built-up sewage gases to escape and pressure in the system to equalize. Figure 6.19 shows a schematic
isometric of a two-bath plumbing system and the various connections and outlets needed.
Plumbing drawings are typically part of the construction-drawing set. In most cases, they are sub-
mitted with the construction drawings for a building-permit application. They are also part of the pack-
age for pricing the project for the client. They are used for construction. All related plumbing lines; drains,
connections, and vents must be installed according to the approved drawings.
A mechanical-engineering company produces the drawings. They must comply with the National
Plumbing Code and with national, provincial, and local codes.
Engineers produce their own drawings. They are based on plans provided by the interior designer
or architect. These plans show the engineer the location of plumbing fixtures such as toilets, sinks, and
water heaters in the design. Some projects require piping for equipment as well.
Generally, the engineer draws a plumbing plan and connection diagrams. Typical diagrams are of
the water-supply system and the sanitary stack. Legends, schedules, and notes specific to the project
are added. On small projects, there are usually only a few fixtures, a sink and a toilet. In this case, the
required information is included on the mechanical-drawing sheets. For large or complex designs, the
plan(s), diagrams, notes, etc., are on separate sheets. Several sheets may be required to cover all the
information. Figure 6.20 shows a plumbing and sprinkler layout plan.
The engineer’s drawings must provide information regarding the connections to the main water and
sanitary sewer lines. The layout of any existing and new piping is indicated on the plan. The size for all
lines for water, sanitary, and venting must be noted. The hookup to the water meter, new or existing, is
covered, and the type, size, and location of the water heater are specified.
The following are typically included in a set of plumbing drawings:
- A plan with lines and symbols representing all piping
- Symbol legend, general notes, and specific key notes
- Fixture schedule, specifying the manufacturer and model for each item
- The sizes for all piping, cold/hot water, sanitary, vent lines, etc.
- Diagrams, such as water riser and sanitary stack
- Information regarding the water heater
Other information may be needed, depending on the complexity of the project:- Details drawings, such as water heater, water-meter connection, or floor drains
- Diagrams or details referencing special equipment requirements
- Fire-protection notes
- Fire-sprinkler notes and symbols
- Special-air lines
- Natural-gas lines