Pipe Marking Guide


The following article provides basic instructions for pipe markers design and placement. These recommended practices will help improve facility efficiency and increase safety through visual communication. Proper pipe marking plays a critical role in protecting the safety of workers, visitors and emergency responders who must enter a facility. The following instructions are designed to help your facility comply with widely accepted standards for pipe marking. Following these standards helps ensure pipe content, flow direction and additional pipe information are easily seen and understood by all.

The goal is to reduce confusion, dangerous situations, injuries and even deaths.

Although the ASME/ANSI standard suggests labeling all pipes, it is required for pipes to be labeled in the following situations:

  • the contents of pipes could affect procedures during emergency situations
  • the contents of pipes are hazardous
  • the flow direction is unknown
  • the destination of the contents is unknown
  • the flow needs to be redirected for maintenance
  • one or more valves need to be shut off for maintenance


Pipe marker location plays a critical role in the safety and efficiency of every facility. In many facilities, pipe systems generally have a number of bends, penetrations, valves and possibly distribution headers. Factor these visual obstacles into your final placement decision. Every pipe must have pipe markers that are visible from any location from which the pipe can be seen.

Labels must always be applied to clean and dry surfaces to provide lasting performance. Visually appropriate locations often need to be cleaned of debris to create an acceptable pipe marker surface.

Pipe markers should be placed:

  • To indicate direction of flow by labeling with arrows at one or both ends of the label;

  • To be visible from the point of normal approach;

  • At any line entry or re-entry point;

  • Near valves, flanges, and changes in pipe direction;

  • At both sides of ceiling, wall, or floor penetrations;

  • On straight pipe runs;

  • Every 25 ft to 50 ft is typical.

Special Conditions for placement:

  • If a pipeline is located above the normal line of vision, the label shall be placed below the horizontal center line of the pipe to maximize visibility;

  • If a pipeline is located below the normal line of vision, the label shall be placed above the horizontal center line of the pipe to maximize visibility.

Pipe Label Size. The size of the pipe marker is also an important factor. Properly sized labels will allow personnel to read the labels at a reasonable distance. See the table below to ensure existing pipe markers are standard-compliant. If not, they should be replaced.

Outside Pipe Diameter Including Covering

Minimum Length of Label Field Color

Minimum Height of Letters

0.75" - 1.25" (19 - 32 mm)

8" (203 mm)

0.5" (13 mm)

1.5" - 2" (38 - 51 mm)

8" (203 mm)

0.75" (19 mm)

2.5" - 6" (64 - 152 mm)

12" (305 mm)

1.25" (32 mm)

8" - 10" (203 - 254 mm)

24" (610 mm)

2.5" (64 mm)

Over 10" (Over 254 mm)

32" (813 mm)

3.5" (89 mm)

NOTE: Pipes too small for labels should be marked with a hanging tag.


The contents of a pipe determines the color scheme of the pipe marker. See the following table to  ensure existing pipe markers are standard compliant. If not, they should be replaced.


Fluids which are a vapor or produce vapors that can ignite and continue to burn in air.

Black on Yellow


Fluids that may burn but are not flammable.

White on Brown

Toxic & Corrosive

Fluids which are corrosive or toxic or will produce corrosive or toxic substances.

Black on Orange

Fire Quenching

Water and other substances used in sprinkler fire fighting piping systems.

White on Red

Other Water

Any other water except for water used in sprinkler & fire fighting piping systems.

White on Green

Compressed Air

Any vapor or gas under pressure that does not fit a category above.

White on Blue

Defined by User

Defined by user.

White on Black

Defined by User

Defined by user.

Black on White

Defined by User

Defined by user.

White on Purple

Defined by User

Defined by user.

White on Gray


Need pipe markers? Evaluate what your facility’s needs are first. If your facility is medium-to-large in size, it may be more cost-effective and efficient to have a Handheld Label Printer in-house. Pipe markers and many other industrial labels can be custom designed and easily printed on demand when employees have access to the right printer and supplies in their work area.

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