Piping System Labeling Scheme

Written by Matt Milbury on . 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