Pipe Marker Color Code Chart: ASME A13.1 Colors Explained:
Walk into any mechanical room and you'll see pipe markers in different colors. Green, yellow, red, orange — they all mean something different.
These colors aren't random. They follow a national standard called ASME A13.1. Once you learn the system, you can read any pipe in any building in seconds.
This guide breaks down every color in the ASME A13.1 system — what it means, when to use it, and which types of pipes it applies to.
Why Pipe Marker Colors Matter
Colors on pipe markers work like road signs. You don't have to read every word to get the message. A yellow/black label says "hazardous" the same way a yellow diamond highway sign says "warning."
In an emergency, this matters a lot. A firefighter, paramedic, or maintenance tech entering an unfamiliar building needs to know instantly which pipes carry dangerous materials. Colors make that possible at a glance — no reading required.
That's the whole point of ASME A13.1. It creates one consistent color system that anyone, in any facility, can understand.
The 7 Core ASME A13.1 Pipe Marker Colors
1. Green / White — Safe Fluids
What it means: The pipe carries a fluid that is low hazard under normal conditions.
Common pipe contents:
- Potable water (drinking water)
- Chilled water supply and return
- Filtered water
- Condensate
- Cold water supply
- Irrigation water
- Boiler feed water
When to use it: Any water or water-based system that doesn't present a significant hazard. These are the most common pipe markers in commercial buildings.
What the label looks like: White text on a green background.
2. Yellow / Black — Hazardous Materials
What it means: The pipe carries a flammable, oxidizing, corrosive, chemically reactive, or otherwise hazardous material.
Common pipe contents:
- Acids (acid, acid vent, acid waste)
- Corrosive liquids
- Flammable gases (in some applications)
- Reactive chemicals
- Glycol (in some applications)
When to use it: Any pipe whose contents could cause injury through fire, chemical reaction, or skin and eye contact.
What the label looks like: Black text on a yellow background. This is the universal caution color — the same as OSHA hazard warning colors.
3. Red / White — Fire Suppression Systems
What it means: The pipe is part of a fire protection system.
Common pipe contents:
- Fire sprinkler water
- Fire protection water supply
- Fire auto sprinkler lines
- Fire suppression supply and return
When to use it: Any pipe that is part of a fire sprinkler, standpipe, or fire suppression system. NFPA 13 also addresses fire sprinkler pipe identification.
What the label looks like: White text on a red background. Easy to spot in an emergency or during inspection.
4. Orange / Black — Toxic / Extra Hazardous Materials
What it means: The pipe carries a material that is toxic or extremely hazardous — even in small amounts.
Common pipe contents:
- Ammonia (refrigeration systems)
- Toxic industrial gases
- Extremely hazardous chemicals
- Some industrial process fluids
When to use it: When the material in the pipe poses a serious health risk even at low exposure levels. Ammonia refrigeration systems are the most common application.
What the label looks like: Black text on an orange background.
5. Blue / White — Low-Hazard Compressed Gases
What it means: The pipe carries a compressed gas that is low hazard — not flammable, not toxic.
Common pipe contents:
- Compressed air
- Nitrogen (industrial applications)
- Argon
- Non-medical vacuum lines
- Non-medical air systems
When to use it: For inert or low-hazard gas lines, most commonly in industrial plants, laboratories, and manufacturing facilities.
What the label looks like: White text on a blue background.
6. Brown / White — Combustible Fuels
What it means: The pipe carries a combustible liquid or fuel.
Common pipe contents:
- Natural gas
- Fuel oil supply
- Fuel oil return
- Diesel
- 2 PSI and 5 PSI natural gas lines
When to use it: Any pipe that carries a fuel that can burn. Gas lines and fuel oil lines always get brown/white markers.
What the label looks like: White text on a brown background.
7. Purple / White — Reclaimed or Non-Potable Water
What it means: The pipe carries reclaimed, recycled, or non-potable water. This is water that has been treated but is not safe to drink.
Common pipe contents:
- Reclaimed water
- Gray water
- Recycled water for irrigation
- Non-potable process water
When to use it: Any system that uses treated water that is not safe for human consumption. This is increasingly common in green buildings and water-conservation systems.
What the label looks like: White text on a purple background.
Quick Reference Color Chart
| Pipe Contents | Correct Color Combo |
|---|---|
| Drinking water | Green / White |
| Chilled water | Green / White |
| Boiler feed water | Green / White |
| Filtered water | Green / White |
| Fire sprinkler water | Red / White |
| Fire protection lines | Red / White |
| Natural gas | Brown / White |
| Fuel oil (supply/return) | Brown / White |
| Diesel | Brown / White |
| Ammonia (refrigerant) | Orange / Black |
| Toxic gases | Orange / Black |
| Acid / acid waste / acid vent | Yellow / Black |
| Corrosive chemicals | Yellow / Black |
| Compressed air | Blue / White |
| Nitrogen | Blue / White |
| Argon | Blue / White |
| Reclaimed water | Purple / White |
| Non-potable water | Purple / White |
What About User-Defined Colors?
ASME A13.1 allows facilities to define their own colors for pipe systems that don't fit the standard categories. These user-defined colors must be documented in the facility's pipe marking plan and communicated to all workers in the building.
If you have a pipe system that doesn't fit any standard category, a custom pipe marker is the right move. You can put any text, color combination, or hazard information on a custom label.
→ Order custom pipe markers at Print Pro AZ
Don't Forget the Flow Direction Arrows
Color tells you what's in the pipe. Arrows tell you which way it's flowing.
ASME A13.1 requires flow direction arrows on all pipe markers. The arrows can be:
- Built into the label — part of the marker design, pointing left or right
- Separate arrow labels — placed next to the text label on the pipe
At Print Pro AZ, we stock standalone arrow labels in all standard ASME A13.1 colors:
- Blue / White Arrow
- Green / White Arrow
- Brown / White Arrow
- Yellow / Black Arrow
- Orange / Black Arrow
- Red / White Arrow
These are perfect for adding flow direction to an existing label system, or for pipes where you only need to show direction without a full text marker.
Common Color Mistakes to Avoid
Using yellow/black for gas lines. Natural gas and fuel oil should be brown/white, not yellow/black. Yellow/black is for corrosive or chemically hazardous materials.
Using green/white for non-potable water. Reclaimed or gray water needs purple/white. Mixing green and purple up is a health hazard and an inspection flag.
Using orange/black for all hazards. Orange/black is specifically for toxic or extra-hazardous materials. Don't use it for general hazardous chemicals — that's yellow/black.
Skipping the arrows. Color tells people what's inside. Arrows tell them which way it flows. Both are required by ASME A13.1.
Using indoor labels outdoors. Colors fade fast in direct sunlight. Always use UV-resistant labels on outdoor pipes or any sun-exposed location.
Shop Pipe Markers by Color at Print Pro AZ
We stock all standard ASME A13.1 color combinations in four label sizes to fit any pipe. Same-day shipping on most orders. Made in the USA.
Frequently Asked Questions
What color are water pipe markers? Standard water pipes use green/white markers per ASME A13.1. If the water is reclaimed or non-potable, use purple/white instead.
What color are natural gas pipe markers? Natural gas pipes use brown/white markers. This applies to all combustible fuel lines, including fuel oil and diesel.
What color are fire sprinkler pipe markers? Fire sprinkler and fire suppression pipes use red/white markers per ASME A13.1 and NFPA 13.
What color are ammonia pipe markers? Ammonia refrigeration pipes use orange/black markers, which indicate a toxic or extra-hazardous material.
What color are acid pipe markers? Acid, acid vent, and acid waste pipes use yellow/black markers — the color combination for hazardous or corrosive materials.
What color are compressed air pipe markers? Compressed air uses blue/white markers, which indicate a low-hazard compressed gas.
Can I use custom colors for unique pipe systems? Yes. ASME A13.1 allows user-defined colors for pipe systems that don't fit the standard categories. Custom pipe markers with any color combination and text are available from Print Pro AZ.