Pipe Color Codes & Identification Standards: ASME A13.1, BS 1710, IS 2379, ISO 20560 & PFI ES-22

1. Fluid Identification vs Material Identification

Most confusion about the term "pipe color code" comes from treating two different systems as one. A plant operator walking a pipe rack needs to know the hazard and contents of a line before opening a valve. A fabrication-shop storeman needs to know whether a spool is A106 Gr. B carbon steel or A335 P22 chrome-moly before it is welded. Each need has its own standard, its own colors and its own point in the project life cycle.

2. PFI ES-22 Pipe Color Code for Piping Materials

PFI ES-22, published by the Pipe Fabrication Institute, is the most widely used recommended practice for identifying piping material grades by color. It is written for fabrication shops, stockists and laydown yards where hundreds of similar-looking spools, fittings and flanges are stored side by side. A single mix-up – for example a carbon steel elbow welded into a P91 high-energy steam line – can cause creep or hydrogen failure years later, so a fast visual check matters.

How PFI ES-22 colors are applied

• Pipe: a continuous longitudinal stripe of paint, dye or tape along the full length, so every cut piece keeps its identity.
• Flanges: a color band on the back of the flange, where the back face meets the hub.
• Fittings: a stripe running from bevel to bevel (elbows, tees, reducers, caps).
• Weld bevels stay clean: paint must not be applied to weld preparation surfaces.
• Paint chemistry: for stainless steel and nickel alloys use markers that are low in chlorides, sulfur and low-melting metals (zinc, lead) to avoid stress corrosion cracking and liquid-metal embrittlement.

Carbon steel and high-yield line pipe

Low-alloy chrome-moly steels

Stainless steels

Nickel alloys and aluminum

3. ASME A13.1 Pipe Color Code and Marking Scheme

ASME A13.1, "Scheme for the Identification of Piping Systems", is the reference for fluid-service pipe marking in the United States and in many oil, gas and power projects worldwide. It is the document OSHA inspectors and US fire codes point to for pipe labels. The current edition is ASME A13.1-2023; the 2020 revision refined definitions, the legend and color sections and added guidance for abandoned piping. The core color scheme introduced in 2007 has not changed.

A compliant ASME marker has three elements: a color field that shows the hazard class, a legend naming the contents (and, where useful, temperature or pressure), and an arrow showing flow direction. GHS hazard pictograms may be added as supplementary information.

ASME A13.1 marker and letter size

Marker size is chosen from the outside diameter of the pipe or insulation jacket, not the nominal bore. For pipe smaller than 3/4 in (19 mm) and for valves and fittings, a permanently attached legible tag is used instead.

4. BS 1710 Pipe Colour Code (UK)

BS 1710:2014 is the British Standard for identifying pipelines and services above and below ground in buildings, industrial plants and ships’ shore installations. It uses a two-level system:

• Basic identification colour – shows the fluid group. It is painted along the whole pipe or applied as a band at each identification point.
• Safety colour or code indication – a narrower band placed between two basic-colour bands to show a specific hazard or service (fire fighting, drinking water, etc.).

All colours are specified by BS 4800 reference numbers, which is what a painting or marker specification should quote. A flow arrow in black or white (whichever contrasts better) and the content name complete the marking.

Band width: BS 1710 scales band sizes to the outside diameter including insulation, so a large insulated line needs wider bands than a small bare pipe. In practice UK marker suppliers offer bands from about 150 mm wide on small pipe up to 600 mm or more on large lines. State the minimum widths in the project painting specification so that contractors do not guess.

5. IS 2379 Pipe Colour Code for Pipeline Identification (India)

IS 2379:1990 from the Bureau of Indian Standards covers identification of fluids in pipelines in buildings and industrial installations that do not already follow a specific industry code. It is common in Indian and South Asian refineries, fertilizer plants and power stations. It excludes buried pipelines and electrical services.

The scheme uses a ground colour (fluid group), applied either over the whole pipe or as a length at each marking point, with one or two narrower colour bands superimposed to identify the exact fluid or its condition. Shades are named to IS 5 (Colours for ready mixed paints and enamels). The content name and a flow arrow are added in a contrasting colour; the standard gives separate arrow sizes for pipes up to DN 200 and above DN 200.

6. ISO 20560-1 Piping Content Marking (International)

ISO 20560-1 was first published in 2020 and revised as a second edition in June 2024, which adjusted several color values (notably yellow and maroon). It is the first truly international standard for marking pipe contents and is increasingly specified on multinational projects in Europe, the Middle East and Asia. Part 2 covers tanks.

An ISO 20560-1 marker combines four elements: an identification color for the content group, the content name (or chemical formula), a flow direction arrow and, for hazardous contents, the relevant GHS hazard pictograms. Supplementary colors and technical data (pressure, temperature) may be added.

7. Pipe Color Code Comparison: ASME vs BS vs IS vs ISO

Use this cross-reference when a project mixes vendors or owners from different regions, or when converting an existing plant from one scheme to another. The colors are not interchangeable – for example, green means water everywhere, but steam is silver-grey in BS 1710 and aluminium in IS 2379, while ASME A13.1 has no dedicated steam color.

8. Where to Place Pipe Color Code Markers

A marker is only useful if someone can see it from where they stand. All the fluid-service standards agree on the same principle: identify every line at points where a person needs to make a decision – at valves, branches, penetrations and at intervals along straight runs.

9. How to Specify a Pipe Marking System for a Project

1. Name the governing standard. Check the contract and owner specification: ASME A13.1 for US-based owners, BS 1710 for UK, IS 2379 for Indian PSU clients, ISO 20560-1 for many international projects. Use one scheme per facility.
2. Build a fluid list. Take every service from the P&ID line list and classify it (flammable, toxic, water, air, user-defined). Steam, condensate and inert gas need an owner decision under ASME A13.1.
3. Size the markers. Use OD over insulation to select marker length and letter height from the size table.
4. Define the legend. Content name, line number if required, and flow arrow. Add GHS pictograms for hazardous fluids where ISO 20560 or owner rules ask for them.
5. Choose marker material. Painted bands for hot or outdoor lines; UV-stable, temperature-rated adhesive or strap-on markers elsewhere. Check compatibility with stainless steel and insulation cladding.
6. Coordinate with the painting spec. Ground or band colors must match the coating system (e.g. ISO 12944) and quote BS 4800, IS 5 or RAL references.
7. Mark placement on drawings. Show marker locations on isometrics or a marking plan: valves, branches, penetrations and intervals.
8. Fabrication control. Separately require PFI ES-22 (or project) material colors in the shop plus PMI for alloys.
9. Maintain and update. Replace faded markers, re-mark after modifications and identify abandoned lines so they are never mistaken for live services.

10. Common Pipe Color Code Mistakes

11. Frequently Asked Questions

12. Test Your Knowledge: Pipe Color Code Quiz

Related Aienginear Guides and Tools

Reviewed: October 2026 by Muhammad Raza, Aienginear. This guide summarizes ASME A13.1-2023, BS 1710:2014, IS 2379:1990, ISO 20560-1:2024 and PFI ES-22 in our own words for education and planning. It is not a substitute for the purchased standards or your project specification, which always govern. Color swatches are screen approximations.