Plumbing drawings provide all pertinent information on the design of the plumbing system for a project, including line sizes and location, fixture location, isolation valves, storage-tank capacities, hot-water-heater capacities and locations, and drain locations and routing. Plumbing systems involve two major components, water supply and drainage. Water is supplied under pressure through pipes to plumbing fixtures. Drainage works by gravity: Drain pipes must slope downward. Vent pipes are required. A plumbing floor plan will typically show the location and type of plumbing fixtures, as well as the route pipes will be run (overhead or through walls) for potable water, drainage, waste, and vents. Plumbing drawings are usually numbered beginning with “P,” as in P-1, P-2, etc.

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 dishwasher. 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 submitted with the construction drawings for a building-permit application. They are also part of the package 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

Isometric diagram of a two-bath plumbing system.

Isometric piping diagrams of hot- and cold-water riser systems.

Engineer’s drawings are required for all commercial projects involving any plumbing work. This applies to additions, renovations, or new construction. A permit is required prior to commencing any work on site.

Building codes specify the number of toilets, urinals, and lavatories required in a building or space, based on the occupancy type. In many cases the facilities must be designed as accessible for the disabled as discussed in Chapter 11. The designer, architect, and engineer must comply with all codes when producing their final drawings.

Floor plan showing plumbing and sprinkler layout.

Drawings and permits are also needed for residential projects when substantial plumbing work is to take place. For small projects, a licensed plumber can submit the information required to obtain a permit.

A professional engineer also provides the required drawings and reports for a septic-tank installation. A sewage permit must be obtained. A septic tank is installed where a sanitary sewage connection to a municipal treatment facility is not possible.

Concept and designs are the first stage of any project. When established, the next stage is construction drawings. Once a floor plan is complete, it is passed over to the mechanical engineer to produce plumbing drawings. The drawings become part of the construction-drawing set.

In some residences and commercial structures, a separate plumbing plan is drawn to show fixtures, water-supply and waste-disposal lines, equipment, and other supply and disposal sources. These isometric drawings are much easier to understand and are invaluable to those responsible for preparing material estimates and to the craftspeople responsible for installing plumbing systems. The mechanical division of a set of construction drawings will include, in addition to plumbing plans and details, drawings for any heating, ventilation, and air-conditioning systems that a building might contain. Frequently, the drawing sheets in the mechanical division are identified by the designating letter M in the title block. However, remember that in the order of drawings, sheets containing heating, ventilation, and air-conditioning drawings will precede those for plumbing.

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