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ASTM A135/A135M is a specification for electric-resistance-welded steel pipe used to convey gas, vapor, water and other liquids. It covers Grade A and Grade B pipe, with requirements for chemical composition, mechanical properties, manufacturing, dimensions and testing.
ASTM A135 pipe is also widely used in water-based fire protection systems. However, ASTM A135 is not exclusively a fire sprinkler standard. It should not be confused with ASTM A795, which is written specifically for fire protection pipe, or with UL Listing and FM Approval, which are separate product certifications.
For engineers and buyers sourcing fire sprinkler pipes, understanding these distinctions is essential. A pipe can comply with ASTM A135 without automatically being UL Listed, FM Approved or suitable for every sprinkler project.
What Does ASTM A135 Cover?
The full title of ASTM A135/A135M is Standard Specification for Electric-Resistance-Welded Steel Pipe. It applies only to pipe made by electric-resistance or electric-induction welding.
The standard covers pipe intended to convey:
- Water
- Gas
- Vapor
- Other liquids
This broad scope allows ASTM A135 pipe to be used in general fluid systems as well as fire sprinkler installations.
The current ASTM scope includes:
- NPS 2 through NPS 30, or DN 50 through DN 750
- Nominal wall thicknesses up to 0.500 inches, or 12.70 mm
- Selected thinner-wall dimensions from NPS 3/4 through NPS 5
- Other dimensions when the pipe meets all remaining requirements of the specification
Standardized pipe dimensions are generally referenced from ASME B36.10M. ASTM A135 establishes material and manufacturing requirements; it does not create an independent pipe-size system.
The intended service should therefore be stated in the purchase order. A pipe’s suitability depends on more than its ASTM designation. Diameter, wall thickness, connection method, design pressure, surface finish and operating conditions must also be considered.
Requirements outside the standard
ASTM A135 compliance alone does not determine:
- The system design pressure
- Whether the pipe is UL Listed
- Whether the pipe is FM Approved
- Whether a particular coating is suitable
- Whether local authorities will approve the pipe
- Whether the pipe is compatible with specific fittings
- Whether it meets a project’s corrosion-control requirements
These conditions must be specified separately.
What Is the Difference Between ASTM A135 Grade A and Grade B?
ASTM A135 includes two material grades. Grade B provides higher minimum tensile and yield strength, while Grade A is specifically identified as suitable for flanging and bending.
Chemical composition
The values below are maximum percentages.
| Element | Grade A | Grade B |
| Carbon | 0.25% | 0.30% |
| Manganese | 0.95% | 1.20% |
| Phosphorus | 0.035% | 0.035% |
| Sulfur | 0.035% | 0.035% |
Mechanical properties
| Property | Grade A | Grade B |
| Minimum tensile strength | 48 ksi / 330 MPa | 60 ksi / 415 MPa |
| Minimum yield strength | 30 ksi / 205 MPa | 35 ksi / 240 MPa |
| Minimum elongation for applicable specimens | 35% | 30% |
| Weld-seam heat treatment | Not generally required | Required or equivalently processed |
| Adapted for flanging and bending | Yes | Not specifically designated |
Grade B’s greater strength does not automatically give every Grade B pipe a higher allowable system pressure. Pressure capacity also depends on outside diameter, wall thickness, temperature, joint type, material condition and the governing design code.
Grade selection should therefore follow the project specification rather than a simple assumption that the stronger grade is always preferable.
Bending and flanging considerations
ASTM identifies Grade A as the grade adapted for flanging and bending. This does not amount to a complete prohibition on cold-bending Grade B, but Grade B should not be selected for extensive forming without checking the fabrication procedure and project requirements.
For threaded or grooved sprinkler piping, the grade must also be considered together with wall thickness and the approved fitting system.
How Is ASTM A135 Pipe Manufactured and Tested?
ASTM A135 pipe begins with flat-rolled carbon steel. The steel is formed into a cylindrical shape before the longitudinal seam is joined by electric-resistance or electric-induction welding.
No filler metal is added to the weld. Heat is generated by electrical resistance at the strip edges, which are pressed together to form the seam.
Steelmaking and pipe forming
The steel may be produced using:
- A basic-oxygen process
- An electric-furnace process
- A combination of the two processes
It may be cast into ingots or continuously strand cast. The resulting flat steel is supplied in individual or continuous lengths for pipe production.
The manufacturing sequence normally includes:
- Steel coil inspection
- Strip forming
- Electric-resistance welding
- Weld-bead control
- Sizing and straightening
- Cutting to length
- Heat treatment when required
- Mechanical and dimensional testing
- Surface finishing and marking
For Grade B pipe, the weld seam must be heat treated or processed in an equivalent manner so that no untempered martensite remains. This requirement controls the condition of the heat-affected zone and reduces the risk of an excessively hard or brittle weld seam.
Required inspection and testing
ASTM A135 includes several inspection and testing requirements.
Chemical analysis
The steel must comply with the specified limits for carbon, manganese, phosphorus and sulfur. The results should be recorded in the material documentation supplied with the order.
Tensile testing
Tensile testing verifies that the pipe meets the minimum yield strength, tensile strength and elongation requirements for its grade.
Flattening testing
A pipe specimen is flattened between parallel plates. The test evaluates the ductility of the pipe body and the integrity of the longitudinal weld.
Cracking, splitting or weld failure before the specified test stage may indicate a material or manufacturing defect.
Hydrostatic testing
Hydrostatic testing checks each applicable pipe length for leakage or structural failure under internal water pressure.
Under permitted ordering conditions, nondestructive electric testing may be used instead of hydrostatic testing. Available methods can include electromagnetic or ultrasonic inspection. When pipe is supplied without the normally required hydrostatic test, the applicable marking and purchase-order provisions must be followed.
Dimensional and visual inspection
Inspection should also confirm:
- Outside diameter
- Wall thickness
- Length
- Straightness
- End preparation
- Weld condition
- Surface defects
- Required pipe markings
A material test certificate should allow the buyer to connect these results to the relevant heat number and production batch.
What Sizes and Pipe Schedules Are Available?
ASTM A135 defines the permitted scope of the pipe, but commercial sizes depend on the manufacturer, production line and intended application.
Schedule 10 and Schedule 40 are common in fire sprinkler systems. Engineered lighter-wall products may also be available when they have the required product listings and project approval.
Common ASME B36.10M dimensions used for ASTM A135 sprinkler pipe include:
| Nominal Pipe Size (NPS) | Outside Diameter (in.) | Schedule 10 Wall (in.) | Schedule 40 Wall (in.) |
| 1 | 1.315 in. | 0.109 in. | 0.133 in. |
| 1¼ | 1.660 in. | 0.109 in. | 0.140 in. |
| 1½ | 1.900 in. | 0.109 in. | 0.145 in. |
| 2 | 2.375 in. | 0.109 in. | 0.154 in. |
| 2½ | 2.875 in. | 0.120 in. | 0.203 in. |
| 3 | 3.500 in. | 0.120 in. | 0.216 in. |
| 4 | 4.500 in. | 0.120 in. | 0.237 in. |
| 6 | 6.625 in. | 0.134 in. | 0.280 in. |
| 8 | 8.625 in. | 0.188 in. | 0.322 in. |
These figures are commonly used standardized dimensions. They should not be treated as confirmation that every size, schedule, grade and end preparation is available from every manufacturer.
Schedule affects more than weight
For the same nominal pipe size, Schedule 40 has a thicker wall and smaller internal diameter than Schedule 10. This affects:
- Pipe weight
- Internal flow area
- Threading suitability
- Handling and installation
- Hanger loads
- Material cost
- Potential pressure capacity
Thinner-wall pipe reduces weight and may simplify installation, but it must be compatible with the selected grooved, welded or mechanical joint.
Schedule 80 should not be specified broadly without checking the actual wall thickness against the scope of ASTM A135 and the manufacturer’s certified production range.
How Does ASTM A135 Compare With ASTM A53 and ASTM A795?
ASTM A135, ASTM A53 and ASTM A795 can all appear in fire sprinkler specifications, but they are not interchangeable in every project.
| Feature | ASTM A135 | ASTM A53 | ASTM A795 |
| Primary scope | ERW pipe for conveying fluids | General black and galvanized steel pipe | Steel pipe for fire protection use |
| Manufacturing methods | ERW only | Seamless, ERW and continuous welded | Seamless, ERW and furnace welded |
| Grades | Grade A and Grade B | Grade A and Grade B | Grade A and Grade B, depending on type |
| Fire sprinkler use | Common | Common | Specifically intended for fire protection |
| Black pipe | Available | Covered | Covered |
| Galvanized pipe | Requires appropriate separate supply requirements | Explicitly covered | Explicitly covered |
| UL/FM status | Separate certification | Separate certification | Separate certification |
| Main advantage | Efficient ERW production and lighter-wall options | Broad availability and general-purpose use | Fire-protection-specific scope |
ASTM A135 and ASTM A795
The main difference is their scope. ASTM A135 is a general ERW fluid-conveyance pipe standard. ASTM A795 is specifically written for black and hot-dip galvanized steel pipe used in fire protection.
ASTM A135 permits only electric-resistance-welded pipe. ASTM A795 can cover several manufacturing types, including ERW and seamless pipe.
Manufacturers often certify a sprinkler pipe to both A135 and A795 when the product meets both standards. Buyers should still check the actual marking and certification documents rather than assuming dual compliance.
ASTM A135 and ASTM A53
ASTM A53 has a broader manufacturing scope. It covers seamless pipe, Type E electric-resistance-welded pipe and Type F furnace-butt-welded pipe.
ASTM A53 also explicitly covers black and hot-dip galvanized products. It remains common for general piping and Schedule 40 sprinkler applications.
The correct standard depends on the pipe type, wall thickness, manufacturing process and project specification. Substituting one standard for another without approval may lead to rejection during submittal review.
How Should ASTM A135 Pipe Be Specified for Fire Protection?
A clear purchase specification should describe the required product rather than listing only “ASTM A135 pipe.”
At minimum, the request for quotation should include:
- ASTM A135/A135M edition
- Grade A or Grade B
- Nominal pipe size
- Wall thickness or pipe schedule
- Required length
- Black, galvanized, painted or epoxy-coated surface
- Plain, threaded, beveled or roll-grooved ends
- Hydrostatic or approved nondestructive testing
- Required pipe marking
- MTC and batch-traceability requirements
- UL Listing requirements
- FM Approval requirements
- Required third-party inspection
- Packaging and shipping conditions
ASTM compliance and product certification remain separate
ASTM A135 describes how the pipe is manufactured and tested. UL and FM assess products under separate certification programmes.
A pipe marked ASTM A135 is therefore not automatically:
- UL Listed
- FM Approved
- Accepted by the project engineer
- Approved by the local authority
- Suitable for every sprinkler connection
- Compliant with every insurance requirement
Buyers should request the current UL or FM certificate and confirm that the exact pipe size, schedule, grade and product designation fall within the certificate’s scope.
Documents should be checked before shipment
A procurement review should include:
- Material test certificates
- Chemical and mechanical results
- Hydrostatic or NDT records
- Dimensional inspection results
- Pipe marking photographs
- Coating or galvanizing records
- UL and FM certificates when required
- Packing lists linked to heat and batch numbers
This documentation is especially important when several pipe sizes or schedules are supplied in one order.
ASTM A135 pipe from Baolai
Baolai manufactures ASTM A135 fire sprinkler pipe in Grade A and Grade B, with black, galvanized, painted and epoxy-coated surface options.
Available end preparations include plain, threaded and roll-grooved configurations. Project-specific sizes, schedules, certifications and inspection requirements should be confirmed in the RFQ so that the supplied pipe matches the approved submittal.
Conclusion
ASTM A135 establishes the material, manufacturing and testing requirements for Grade A and Grade B electric-resistance-welded steel pipe. Its efficient ERW production and compatibility with commonly used sprinkler pipe dimensions make it a practical option for many fire protection systems.
The designation alone, however, is not a complete project specification. Buyers must also confirm dimensions, wall thickness, ends, coating, test records and any required UL or FM certification. Careful specification prevents an ASTM-compliant pipe from being rejected for failing a separate project or certification requirement.
Frequently Asked Questions
Is ASTM A135 pipe always ERW?
Yes. ASTM A135 applies specifically to electric-resistance-welded or electric-induction-welded steel pipe. It does not cover seamless pipe.
Is ASTM A135 Grade B stronger than Grade A?
Grade B has higher minimum yield and tensile strength. However, this does not automatically mean every Grade B pipe has a higher pressure rating. Diameter, wall thickness, temperature and joint design must also be considered.
Can ASTM A135 pipe be used for fire sprinkler systems?
Yes. ASTM A135 ERW pipe is commonly used in water-based fire sprinkler systems. Its acceptance depends on the project specification, product listing, system design and local approval requirements.
Does ASTM A135 mean that a pipe is UL Listed or FM Approved?
No. ASTM A135 compliance, UL Listing and FM Approval are separate designations. The manufacturer must provide certification covering the exact product when UL or FM approval is required.
Is ASTM A135 the same as ASME SA-135?
ASTM A135 and ASME SA-135 are technically related specifications used under different standards organizations and code frameworks. The project documents should state which designation and edition are required rather than treating them as automatically interchangeable.
