Piping System Labeling Scheme

Written by Matt Milbury. Posted in Pipe

Reasons for Labeling

ASME 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

ASME A13.1 Color Scheme

Fluid ServiceColor Combinations
Fire Quenching Fluids Safety Red Background / White Legend
Toxic & Corrosive Fluids Safety Orange Background / White Legend
Flammable Fluids Safety Yellow Background / Black Legend
Combustible Fluids Safety Brown Background / White Legend
Potable, Cooling, Boiler Feed, & Other Water Safety Green Background / White Legend
Compressed Air Safety Blue Background / White Legend
Defined by the User Safety Purple Background / White Legend
Defined by the User Safety White Background / Black Legend
Defined by the User Safety Gray Background / White Legend
Defined by the User Safety Black Background / White Legend

ASME A13.1 Pipe Label Size

  • To be read from a distance by personnel, the proper sized labels should be used.
  • Pipes too small for labels should be marked with a hanging tag.
Outside Pipe Diameter

Including Covering

Minimum Length of

Label Field Color

Minimum Height of


3/4" - 1 1/4" 8" 1/2"
1 1/2" - 2" 8" 3/4"
2 1/2" - 6" 12" 1 1/4"
8" - 10" 24" 2 1/2"
Over 10" 32"

3 1/2"


  • ASME Standards
    • ASME A13.1 - Scheme for the Identification of Piping Systems