ANSI Pipe Marking Colors Standards

ANSI color code for pipe marking

With the first and latest update in many years, the 2007 edition of the ANSI/ASME A13.1 changed the color coding requirements for the labels and markers on pipes. They added some new colors in this new edition of the pipe marking standards. The new label color requirements are based on the characteristic hazards of what is in the pipe you are marking. See below!

Industrial Pipe Marking Color Chart

YellowFlammable Fluids
RedFire Quenching Fluids
OrangeToxic/Corrosive Fluids
GreenPotable, Cooling, Boiler-Feed, and Other Water
BlueCompressed Air
BrownCombustable Fluids
Purple[Definable by User]
Black[Definable by User]
White[Definable by User]
Gray[Definable by User]

* Source ANSI/ASME A13.1


Correct Placement of Labels

You need to place labels in a way that they can be seen from the ground easily. Employees need to be able to look at a pipe and know its contents directly facing them. Labels should affixed be near valves, branches, splits, near changes of direction, or at the entry and exit points in a room. Recommended spacing would be no greater than 20 feet on a straight run of pipe. See below for more information.

Pipe DiameterMinimum Label LengthMinimum Letter Height
0.7″ – 1.3″8″.5″
1.4″ – 2.4″8″.7″
2.5″ – 6.7″12″1.3″
6.8″ – 10″24″2.5″
> 10″32″3.5″

Pipe Marking labels must effectively communicate the contents of the pipes and give additional detail if special hazards (such as extreme temperatures or pressures) exist.

When marking your pipes, there are 4 key areas where labels should be placed:

  • At 25 to 50 foot intervals on straight runs
  • At all changes in direction
  • On both sides of entry points through floors and walls
  • Adjacent to all flanges and valves
TIP: Labels should be applied at such an angle so that they are easily visible from employees’ direct line of sight. (fig a)


  • ASME A13.1-2007 Scheme for the Identification of Piping Systems, NY 10016
  • ANSI Z53.1-1979 Safety Color Code for Marking Physical Hazards, NY 10036

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