About Pipe Identification

Written by emily beach
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About Pipe Identification
(Wiki Commons)

Pipe labelling standards are developed by the American Society of Mechanical Engineers (ASME). ASME Standard A13.1 describes how pipes should be labelled, including colours, text, and location. Having one standardised system for this procedure helps lower the risk of injury, leaks, and spills during maintenance and renovations. Though A13.1 was updated in 2007, many installers still use a later version from 1996, which contains nearly all of the same requirements. ASME is part of the American National Standards Institute (ANSI), so labelling standards may sometimes be shown as ANSI A13.1 instead. In fact, ANSI accredits and tests the standards developed by its member organisations, and does not create codes or regulations of its own. While both of these groups are US based, many international countries rely on the standards they create.

Label Colors

ASME A13.1- 1996 divides pipes into three basic categories, with a different coloured label used for each. Materials that are hazardous by their very nature should have a yellow label with black text. Examples of hazardous materials include those that are flammable, explosive, chemically reactive, or radioactive. The second category of materials is those that are low hazard. This category is broken down into liquids, which should have a green label, and gases, which should have a blue label. Finally, fire suppression materials like water, Halon, or foam should be marked with a red label. These colours have been the standard system for many decades, though the 2007 edition of A13.1 added two additional colours. Toxic fluids should be marked with an orange label, while combustible fluids should be marked with a brown label. It is important to be familiar with both the 1996 and 2007 systems, as most pipes you'll encounter will be marked under the older of the two.

Text Color and Size

All pipe identification labels should include white text, with the exception of yellow labels, which should have black text. The size of the text is determined by the outside diameter of the pipe, including any insulation or covers. For pipes smaller than 2 inches (51mm), text should be 3/4 inches (19mm) tall. For pipes larger than 2 inches (51mm) but smaller than 6 inches (150mm), text should be 1-1/4 inches (32mm) tall. Pipes between 8 and 10 inches (200 to 250mm) should show text 2-1/2 inches (64mm) tall, while pipes over 10 inches (250mm) should feature text 3-1/2 inches (89mm) tall.

Label Size

When it comes to the size of the label, ASME standards refer to the length of the coloured portion of the label. Pipes smaller than 2 inches (51mm) in diameter should have labels that are at least 8 inches (200mm) long. Pipes ranging from 2-1/2 inches to 6 inches (64 to 150mm) must have labels that are at least 12 inches (300mm) long, and pipes between 8 and 10 inches in diameter should feature labels 24 inches (600mm) in length. Finally, pipes over 10 inches must be equipped with labels longer than 32 inches (800mm).

Location of Labels

Pipe identification labels should be placed on the pipe so that they are easy to locate and read. For pipes located at ceiling level, labels should be on the bottom of the pipe. This way, installers or maintenance workers can see the labels from the ground. Pipes installed below grade or along the floor should be labelled on top, making the label easy to access. ASME recommends that the labels are placed near valves or in convenient spots. This may include the area where a pipe enters a room or where branches or splits occur.


For larger pipe labels, the colour and text is often spray painted onto the pipe using a stencil. With smaller pipes, a typical labelmaker may be used. Pipe labels are made of self-adhesive vinyl or plastic tape, though some may be made of thicker plastic sections that are not self-adhesive. Many pipe marking companies sell labels that are pre-printed with common pipe contents, and also feature directional arrows to show the direction of flow.

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