1 Scope
NOTE This standard establishes requirements for the field identification of aboveground plumbing piping systems so that operators, maintenance staff, contractors, and emergency responders can determine a pipe's contents and direction of flow at a glance, without consulting drawings. (1.1)
NOTE The systems covered are domestic cold water, domestic hot water, hot water recirculation, sanitary waste and vent, storm drainage, non-potable reuse water, reclaimed/recycled water, and interior building natural gas distribution piping not separately addressed by a dedicated standard. (1.2)
NOTE Identification under this standard means the legible labeling of pipe contents and flow direction; it is distinct from pipe insulation jacket color, which is a thermal and weather-protection requirement governed separately. (1.3)
NOTE ASME A13.1 governs aboveground piping only. Buried piping is identified by tracer wire and warning tape under the sitework and utility standards and is outside this scope. (1.4)
1.5Plumbing piping identification shall comply with ASME A13.1-2023 for label color scheme, legend text, letter height, marker length, flow-arrow provision, and placement spacing.
1.6Where the Authority Having Jurisdiction or an owner-published piping identification standard imposes requirements more stringent than ASME A13.1-2023, the more stringent requirement shall govern.
1.7Where this standard conflicts with a dedicated discipline standard for a system that crosses into plumbing scope, the dedicated standard shall govern for that system.
2 Referenced Standards
2.1Materials, labels, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
| Standard |
Title |
| ASME A13.1-2023 |
Scheme for the Identification of Piping Systems |
| ICC IPC-2024 |
International Plumbing Code |
| IAPMO/ANSI UPC 1-2024 |
Uniform Plumbing Code |
| NFPA 99-2024 |
Health Care Facilities Code |
| ANSI Z535.1-2017 (R2022) |
Safety Colors |
| ASTM D2239 |
Polyethylene (PE) Plastic Pipe (SIDR-PR) Based on Controlled Inside Diameter |
NOTE ASME A13.1-2023 is the current edition and supersedes the 2020 edition. The 2023 edition revised color-category designations and aligned hazardous-content marking with GHS pictogram provisions; specifying a superseded edition is a common defect. (2.3)
NOTE The IPC does not publish a detailed pipe-label spacing table; it requires manufacturer identification on pipe materials and marking of condensate terminations, and pipe identification systems are brought in by reference to ASME A13.1 or by this specification. (2.4)
NOTE The UPC, adopted in many western states, requires non-potable water piping to be permanently identified with a continuous purple color distinguishable from potable piping and references the ASME A13.1 color scheme. (2.5)
NOTE NFPA 99 governs medical gas piping identification separately with gas-specific color coding; it sets the boundary between medical gas labeling and general plumbing labeling in health care occupancies. (2.6)
3 Submittals
3.1The Contractor shall submit the following product data and shop documentation for review before any pipe markers or valve tags are procured:
- Manufacturer product data for each pipe marker type, including substrate material, adhesive or fastening method, color, legend text, letter height, and marker length, cross-referenced to pipe outside diameter.
- A complete legend schedule listing every piping system on the project with its assigned legend text, background color, and text color.
- Product data for valve tags, including material, diameter, attachment method, and stamped or engraved legend format.
- A draft valve schedule keyed to the plumbing riser diagram, listing each tagged valve by number, system, service, and location.
- Manufacturer durability and environmental ratings for markers proposed in wet, high-humidity, chemically exposed, or outdoor locations.
☐ Pipe marker product data (substrate, legend, sizing)
☐ Project legend schedule (text and colors per system)
☐ Valve tag product data
☐ Draft valve schedule keyed to riser diagram
☐ Durability/environmental ratings for wet and outdoor markers
3.2The Contractor shall submit the following at closeout:
- A final valve schedule reflecting as-installed valve numbers and locations, formatted for inclusion in the O&M manual.
- Operation and maintenance data describing marker and tag replacement procedures and sources for replacement components.
☐ Final as-installed valve schedule for O&M manual
☐ Marker and tag replacement and source data
4 Quality Assurance
4.1The pipe-marker installer shall be the same trade installing the plumbing piping, or a specialty firm regularly engaged in pipe identification work.
4.2All markers and tags on a project shall be furnished by a single manufacturer to maintain consistent color, legend style, and durability.
4.3Legend text on field markers shall match the system abbreviations and names used on the plumbing riser diagram and in the valve schedule.
NOTE A mismatch between field legend text and the riser-diagram or O&M abbreviations is a frequent source of operator confusion. (4.4)
4.5Legend text shall be reconciled against the riser-diagram and O&M abbreviations before markers are ordered.
4.6Before ordering, the Contractor shall verify with the Authority Having Jurisdiction whether continuous-color pipe material satisfies non-potable identification or whether labels are additionally required.
5 Environmental and Service Conditions
5.1Marker substrate and adhesive shall be selected for the installed environment.
NOTE Indoor conditioned spaces, mechanical rooms with condensation, chemically exposed areas, and exposed outdoor runs each impose different durability demands, and a single generic marker rarely suits all of them. (5.2)
NOTE Self-adhesive vinyl markers specified for high-humidity, condensing, or chemically exposed locations without a moisture- and chemical-resistant substrate peel and fail within months; selecting the substrate to match the installed environment is what keeps markers readable through the warranty period. (5.3)
5.4Markers in outdoor or wet locations shall be UV-resistant and moisture-resistant with a minimum rated outdoor service life of five years.
5.5Markers on or over pipe insulation shall be applied to the finished insulation jacket surface; insulation jacket color shall not be used as a substitute for an ASME A13.1-compliant marker.
● Indoor conditioned (dry)
○ Mechanical room (humid/condensing)
○ Chemically exposed (treatment/process area)
○ Outdoor or wet (UV exposure)
6 Identification Schedule
6.1Every aboveground plumbing piping system on the project shall be identified.
NOTE The schedule below establishes which systems require markers and the default ASME A13.1-2023 color assignment for each. (6.2)
6.3Each piping system listed in the project schedule shall be identified with markers bearing the legend text, background color, and text color assigned to that system.
6.4Domestic cold water and domestic hot water piping shall be identified with a green background and white text per the ASME A13.1-2023 water (potable) category.
6.5Domestic hot water recirculation piping shall be identified with the same potable-water color scheme as domestic hot water and shall carry the legend distinguishing it as recirculation.
6.6Non-potable reuse, reclaimed, and recycled water piping shall be identified with a purple background and white text.
6.7Building natural gas piping shall be identified with a yellow background and black text per the ASME A13.1-2023 flammable-gas category.
6.8Sanitary waste, vent, and storm drainage piping shall be identified with a black background and white text as a user-defined category.
● ASME A13.1-2023 standard color scheme
○ Owner-published color standard (supplements A13.1)
Green background / white text - DOMESTIC COLD WATER
Green background / white text - DCW
Green background / white text - DOMESTIC HOT WATER
Green background / white text - DHW 140°F
Green background / white text - DHW 120°F
Green background / white text - DHW RECIRC
Green background / white text - HW RECIRCULATION
Purple background / white text - RECLAIMED WATER - DO NOT DRINK
Purple background / white text - NON-POTABLE WATER
Purple background / white text - RECYCLED WATER
Yellow background / black text - NATURAL GAS
Yellow background / black text - GAS
Black background / white text - SANITARY WASTE
Black background / white text - VENT
Black background / white text - STORM DRAIN
7 Legend Content
NOTE The legend is the text printed on the marker; over-abbreviation defeats the purpose — a marker reading "DCW" helps no one outside the design team. (7.1)
7.2The legend shall state the system's contents in a form an operator who has never seen the drawings can read and act on.
7.3Each marker legend shall state the pipe contents using the common system name assigned in the project legend schedule.
7.4Where space on small-diameter pipe forces abbreviation, the abbreviation shall be drawn from the project legend schedule and used consistently across the project.
7.5Reclaimed, recycled, and non-potable water markers shall include a "DO NOT DRINK" or equivalent caution legend in addition to the system name.
7.6Markers may include service data such as temperature or pressure where the owner or Engineer of Record requires it; service data shall not replace the contents name.
● Full common name (e.g. DOMESTIC COLD WATER)
○ Abbreviated name (e.g. DCW) - small pipe only
○ Common name with service data (e.g. DHW 140°F)
● No
○ Yes - temperature
○ Yes - pressure
○ Yes - temperature and pressure
8 Marker and Letter Sizing
NOTE ASME A13.1-2023 sizes the marker by the pipe outside diameter, including any insulation: larger pipe gets larger letters and a longer color band so the marker is legible from the distances at which large mains are typically viewed. (8.1)
8.2Outside diameter for sizing purposes shall be measured over the finished insulation jacket where the pipe is insulated, not over the bare pipe.
8.3Minimum letter height and minimum color-band (marker) length shall be selected from the table below based on the pipe outside diameter including insulation.
| Pipe OD including insulation |
Min. letter height |
Min. marker length |
| 3/4" to 1-1/4" |
1/2" |
8" |
| 1-1/2" to 2" |
3/4" |
8" |
| 2-1/2" to 6" |
1-1/4" |
12" |
| 8" to 10" |
1-3/4" |
24" |
| Over 10" |
2-1/2" |
32" |
8.4Letter height and marker length below the tabulated minimum for the pipe outside diameter shall not be accepted.
● ASME A13.1-2023 Table by pipe OD (including insulation)
○ Owner standard (if more stringent)
9 Flow Direction Arrows
NOTE A marker without an arrow tells an operator what a pipe carries but not which way it moves; for isolating, draining, and tracing a system the direction is as important as the contents. (9.1)
9.2Each pipe marker shall include at least one flow-direction arrow indicating the direction of normal flow.
9.3Where flow reverses or recirculates, such as on hot water recirculation returns, the marker shall bear a bidirectional arrow or shall be labeled to indicate the reversing condition.
9.4Flow arrows shall point in the actual installed direction of flow; arrows shall be verified against the system before marker placement.
● Single direction (normal flow)
○ Bidirectional (recirculation / reversing)
10 Placement and Spacing
NOTE Markers are placed where an operator will be looking when they need the information: at the devices they operate, at the points where a pipe changes identity or disappears, and at intervals close enough that a marker is always within sight along a run. (10.1)
10.2Markers shall be installed so that at least one marker is visible from any normal operating or maintenance approach to the piping.
10.3On straight runs, markers shall be spaced at intervals not exceeding 25 ft (7.6 m).
10.4A marker shall be installed at each valve, on both the upstream and downstream sides where both are accessible.
10.5A marker shall be installed at each branch and tee, on each leg of the fitting.
10.6A marker shall be installed on both sides of every wall, ceiling, and floor penetration.
NOTE Labeling only one side of a penetration leaves the concealed run unidentified and is a recurring inspection and punchlist finding. (10.7)
10.8Both sides of every wall, ceiling, and floor penetration shall be labeled.
10.9A marker shall be installed within 6" of each connection to equipment, including water heaters, mixing valves, pressure-reducing valves, backflow preventers, and interceptors.
NOTE Equipment connections at water heaters, mixing valves, and pressure-reducing valves are frequently missed by installers and flagged at final inspection; placement at these connections shall be verified during installation. (10.10)
☑ Both sides of each valve (where accessible)
☑ Each leg of every branch and tee
☑ Both sides of wall/ceiling/floor penetrations
☑ Within 6" of each equipment connection
☑ Straight-run intervals not exceeding the maximum spacing
11 Marker Type and Material
NOTE Marker construction is chosen for the pipe size, the surface, and the environment. Wrap-around adhesive markers suit small clean pipe; snap-on markers suit insulated or high-moisture pipe; stencil-and-paint suits large mains; and on-site printed laminated labels allow custom legends and valve numbering. (11.1)
11.2The marker type for each system and location shall be selected from a single coordinated product family so that color and legend style remain consistent across the project.
11.3Self-adhesive wrap-around markers shall be applied only to clean, dry pipe surfaces within the marker's rated environment.
11.4Snap-on clamp-style markers shall be used where adhesion is unreliable, such as on insulated pipe or in high-moisture locations.
11.5Stencil-and-paint identification, where used on large-diameter mains, shall be applied per a field execution protocol that produces letter heights and color bands meeting the sizing table.
● Self-adhesive vinyl wrap-around (pre-printed, UV-resistant)
○ Snap-on plastic clamp marker (insulated/high-moisture)
○ Laminated polyester printed on-site (custom legend)
○ Stencil and paint (large-diameter mains)
● Standard indoor vinyl
○ UV- and moisture-resistant laminated polyester
○ Chemical-resistant laminate
12 Reclaimed and Non-Potable Water Identification
NOTE Reclaimed and non-potable water carries a public-health risk if mistaken for potable supply, so its identification is reinforced beyond ordinary labeling: a purple pipe color or purple banding, the standard purple-background marker, and a caution legend together make a cross-connection error far less likely. (12.1)
NOTE The purple-pipe convention for reclaimed and recycled water is both an industry-wide convention and, under the UPC and several state codes, a code requirement; omitting it on projects with reclaimed water, rainwater harvesting, or greywater reuse is a code violation. (12.2)
NOTE Some states, including California, Florida, and Texas, impose prescriptive reclaimed-water pipe color and identification rules that go beyond the ASME A13.1 default; the applicable state rule shall be verified for the project location. (12.3)
12.4Reclaimed, recycled, and non-potable reuse water piping shall be identified with continuous purple pipe color or continuous purple banding in addition to purple-background markers, unless the Authority Having Jurisdiction accepts one method alone in writing.
12.5Where continuous-color pipe material is used to satisfy purple identification, the material shall be a recognized purple-pigmented product such as purple PVC or purple polyethylene rated for the service.
12.6Marker spacing on reclaimed and non-potable water piping shall not exceed the straight-run spacing required for potable systems and shall additionally place a caution marker at each point of access.
● Continuous purple pipe color plus purple markers
○ Purple banding plus purple markers
○ Purple markers only (AHJ-accepted)
None beyond ASME A13.1 / UPC default
California prescriptive purple-pipe rule
Florida prescriptive reclaimed-water rule
Texas prescriptive reclaimed-water rule
Other state-specific rule
Per drawings
NOTE A pipe marker says what flows through a pipe; a valve tag says which numbered valve this is, so an operator can find "the cold water isolation for the third floor" from the schedule rather than tracing pipe. Without tags and a schedule, maintenance staff cannot reliably locate shutoffs after construction. (13.1)
NOTE Omitting valve tags and the valve schedule from the specification leaves the contractor no deliverable and the owner no way to identify shutoffs post-construction; without both, maintenance staff cannot reliably locate or operate valves after construction handoff. (13.2)
13.3Each accessible shutoff, isolation, control, and drain valve shall be identified with a permanently attached numbered valve tag.
13.4Valve tags shall be brass, aluminum, or engraved laminated plastic, attached with a non-corroding chain or fastener.
13.5Each valve tag number shall correspond to an entry in the project valve schedule giving the valve's system, service, normal position, and location.
13.6The valve tag numbering format shall be coordinated with the plumbing riser diagram and the O&M manual and shall follow the owner's standard format where one exists.
13.7The valve schedule shall be delivered as a closeout submittal and incorporated into the operation and maintenance manual.
● Stamped brass disc
○ Stamped aluminum disc
○ Engraved laminated plastic (lamacoid)
● Discipline-system-sequence (e.g. P-CW-101)
○ Owner-standard format
○ Sequential project number
Per drawings
14 Installation
14.1Markers shall be installed only after pipe insulation, painting, and any jacketing is complete, so that the marker is applied to its final visible surface.
14.2Markers shall be oriented so the legend reads from the normal operating and approach position, with the legend on the lower half of pipe viewed from above and on the upper half of pipe viewed from below where the approach direction is fixed.
14.3Adhesive markers shall be applied to surfaces cleaned and dried per the marker manufacturer's instructions to achieve full bond.
14.4Valve tags shall be attached so they remain with the valve through normal operation and do not interfere with valve actuation.
14.5Markers and tags damaged, soiled, or rendered illegible during construction shall be replaced before substantial completion.
15 Inspection
NOTE Before substantial completion the Contractor shall walk the installed identification with the Engineer of Record or owner to confirm completeness against the schedule and placement rules. (15.1)
15.2The Contractor shall verify that every system in the identification schedule is labeled with the assigned legend text and colors.
15.3The Contractor shall verify that markers are present at all valves, branches, penetrations, and equipment connections and at the required straight-run intervals.
15.4The Contractor shall verify that every tagged valve appears in the final valve schedule and that schedule locations match the field.
15.5Deficiencies found during inspection shall be corrected and re-inspected before the identification work is accepted.
16 Delivery, Storage, and Handling
16.1Markers, tags, and stencils shall be delivered in the manufacturer's original packaging with legend, color, and size identification intact.
16.2Markers and tags shall be stored indoors in a dry location and protected from UV exposure until installation.
16.3Adhesive-backed markers shall be kept within the manufacturer's rated temperature and humidity range during storage to preserve adhesion.
17 Warranty
17.1The Contractor shall warrant that markers and tags remain legible and adhered for the project warranty period under the service conditions specified.
17.2Markers that delaminate, fade below legibility, or detach within the warranty period under normal service shall be replaced at no cost to the owner.
18 Spare Parts
NOTE The Contractor shall furnish spare pipe markers and valve tags so the owner can replace damaged identification without a special order. (18.1)
18.2The Contractor shall furnish spare wrap-around markers for each system color and size used, in the quantity specified below.
18.3The Contractor shall furnish blank valve tags and the attachment chain or fasteners in the quantity specified below for future valve additions.