What are the different standards of pipe marking?

When it comes to pipe markings in the workplace, there is really one major set of standards that is used in virtually all locations. This set of standards has been developed by ANSI/ASME, and is what is recommended by OSHA. The standards are updated as needed when there are changes to technologies or systems associated with pipes, but compared to many other areas, the standards are fairly stable. Learning about the different standards listed by ANSI/ASME will help ensure you know how to plan out your overall pipe marking strategy.

Most Common Pipe Marking Color Standards

When it comes to pipe markings, the colors used on the markings themselves are one of the most important standards to follow. This is because the colors used can quickly convey the most important information to people, even if they aren’t close enough to read the text on the labels. The standards used across different industries for pipe marking colors are as follows:

  • Yellow – Flammable or oxidizing gasses or fluids
  • Red – Fluids used to put out fires
  • Orange – Toxic or corrosive gasses or fluids
  • Green – Any type of water
  • Blue – All pipes that transport air
  • Brown – Combustible gasses or fluids

Other colors can also be used in pipe markings, but they are considered ‘user defined’ so there isn’t a standard followed throughout different industries. One standard should be used throughout a company, however, even if there are multiple different locations.

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Common Symbols on Pipe Markings

The most common symbols that can be seen on pipe markings are arrows that denote the directional flow of the pipe's contents. However, A13.1 does allow for the use of GHS pictograms on pipe markings if there is a holding container nearby with the corresponding standard GHS label. The addition of these details is just an extra precaution for employees as there is never too much information when regarding hazardous chemicals. With that being said, there are a few requirements the user must abide by for the label to be compliant if this route is taken, those additions include:

  • The name of the chemical/identifier
  • The signal word
  • The appropriate pictogram(s)
  • A hazard statement

Standard for When Markings Should be Used

Identifying where the markings should be placed on the pipes is another important thing to understand. There are a variety of different locations that will require a marking. Depending on the length of the piping, it can be necessary to have multiple markings. The standards to follow are:

  • Distance Between Markings – On straight runs of pipe, there should be a marking placed ever 25’ to 50’ depending on visibility.
  • Changes of Direction – Anytime a pipe changes directions, a marking should be placed on either side of the direction change.
  • Entry/Exit Points – Anywhere that a pipe goes through a wall or floor, markings need to be applied to the pipe on both sides of the obstruction.
  • Valves & Flanges – Any valves, flanges, or other changes in the piping will require a marking on each side.

All of these standards are in place to ensure the markings can be seen as easily as possible. When done correctly, those in the area will be able to get the information they need quickly.

Pipe Marking Size Standards

Pipes come in many different sizes, which makes it necessary to have all different sized pipe markings as well. The following are the different standards when it comes to pipe marking size requirements:

  • 0.7’’ to 1.3’’ – These pipes should have markings that are at least 8’’ in length and have a letter height of at least .5’’
  • 1.4’’ to 2.4’’ – This size pipe also requires markings at least 8’’ in length, but the letter height should be at least 0.7’’
  • 2.5’’ to 6.7’’ – Pipes of this size need to have at least 12’’ markings with a letter height of at least 1.3’’
  • 6.8’’ to 10’’ – Pipes at this size need 24’’ markings with 2.5’’ lettering at a minimum
  • Over 10’’ – All pipes this large should have markings at least 32’’ in length and letters at least 3.5’’ in height

Understanding and following all the pipe marking standards will help to keep facilities safe, and also minimize issues when performing maintenance on the pipe system. Make sure the pipes, and their markings, are always kept clean and visible for easy use.


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