AWWA C207 Flange: Classes, Dimensions, Pressure Ratings & ASME Compatibility Guide

If you are specifying flanges for a municipal water pipeline, pump station, or water treatment facility in North America, AWWA C207 is almost certainly the standard you need. But for engineers and procurement teams outside the United States - or those working on projects that mix waterworks and industrial piping - the four flange classes, the dimension tables, and especially the question of compatibility with ASME B16.5 flanges can be genuinely confusing.

This guide covers everything you need to know about AWWA C207 steel flanges: what the standard covers, how Class B, D, E, and F differ from each other, full dimension tables in both inches and millimetres, and - most importantly - a size-by-size compatibility chart showing exactly where AWWA C207 and ASME B16.5 flanges can and cannot be used together. 

AWWA stands for the American Water Works Association, a non-profit organization founded in 1881 that develops standards for water supply and distribution infrastructure across North America. In the context of piping, 'AWWA' refers to a family of standards governing pipes, fittings, flanges, and related components specifically designed for potable water and water treatment service.

AWWA C207 is the specific standard covering steel ring flanges for waterworks service. It defines the design, materials, dimensions, pressure ratings, and testing requirements for slip-on and blind flanges used in large-diameter water pipelines - sizes that ASME B16.5 does not cover or is not optimized for.

• Size range: NPS 4 to NPS 144 (DN 100 to DN 3600) 
• Flange types: Slip-On Ring, Slip-On Hub, and Blind 
• Pressure classes: Class B, Class D, Class E, Class F 
• Material: Carbon steel (no specific grade required, must meet minimum mechanical properties) 
• Face type: Flat Face (FF) for all classes; Class F also available with Raised Face
• Temperature: Ratings applicable at atmospheric temperature only 

Two related AWWA standards are worth knowing: AWWA C110 covers ductile iron and gray iron flanges (commonly found on valves and pumps), and AWWA C228 covers stainless steel flanges for waterworks. C207, C110, and C228 share similar dimensional logic and are designed to work together in the same water system.

The single most important thing to understand about AWWA C207 is its class system. Unlike ASME B16.5, which uses numbered pressure classes (150, 300, 600...), AWWA C207 uses lettered classes - and the letters are not sequential in terms of pressure rating. Here is the complete overview:

In our experience, Class D accounts for roughly 70–75% of AWWA C207 orders we receive for export projects. Class F comes in second for pump station packages. Class B and Class E together make up the remainder - Class B for low-cost buried installations, Class E for specific large-diameter engineering requirements.

All AWWA C207 dimensions are specified in inches. The metric (mm) equivalents below have been converted for reference, as many international projects require both. Dimensions shown are for Class D - the most commonly specified class.

All AWWA C207 dimensions are specified in inches. The metric (mm) equivalents below have been converted for reference, as many international projects require both. Dimensions shown are for Class D - the most commonly specified class.
 

Class D Flange Dimensions (NPS 4" to NPS 48") | D级法兰尺寸表(4"–48")

Note: Dimensions per AWWA C207 (current edition). mm values are converted from inch originals. For sizes NPS 54" to NPS 144", and for Class B, E, F dimension tables, contact CNCJ for the complete reference sheet.

Flange weight is a function of outside diameter, flange thickness, and material density. The reference weights below are for Class D carbon steel flanges (density approx. 7.85 kg/dm³). Actual weights vary with material grade, face type, and hub configuration.

Weights are approximate for Class D slip-on ring flanges in carbon steel. Hub flanges and Class E/F flanges will be heavier. Contact CNCJ for certified weight calculations.

This is the question that causes the most confusion on mixed-standard projects: can AWWA C207 flanges be bolted directly to ASME B16.5 flanges? The answer depends entirely on the specific size and class combination - and the answer changes at different size ranges. This is the size-by-size breakdown that most guides do not provide. 

Important: Even where bolt patterns match (NPS 4"–24"), full interchangeability requires matching face type and gasket. AWWA C207 uses flat face with full-face gaskets; ASME B16.5 uses raised face with ring gaskets. Mating a raised-face ASME flange to a flat-face AWWA flange without a flat-face adapter risks gasket damage and seal failure. Class F (which can be raised face) is the exception.

The most common mistake we see in mixed-standard projects is assuming that matching pressure class (AWWA Class D ≈ ASME Class 150) means the flanges are interchangeable. They bolt up in the same hole pattern up to NPS 24 - but the face type mismatch means the gasket selection is completely different. Always specify the correct full-face gasket when mating AWWA to ASME flanges, and confirm with your gasket supplier.

Unlike ASME B16.5, which specifies exact material grades (A105, A182 F316, etc.), AWWA C207 does not mandate a specific steel grade. Instead, it requires the flange material to meet minimum mechanical property thresholds:

• Minimum yield strength: 30,000 psi (207 MPa) 
• Minimum tensile strength: 60,000 psi (414 MPa) 
• Minimum elongation: 21% in 8 inches

In practice, the most commonly used material for AWWA C207 flanges is ASTM A36 or ASTM A105 carbon steel. For corrosive water environments or seawater desalination applications, stainless steel versions (304/316L) are produced to AWWA C228 - the stainless steel equivalent of C207.

For water treatment applications, flanges often require internal lining or external coating. Fusion-bonded epoxy (FBE) coating is the most common surface treatment specified for buried AWWA flanges, providing corrosion protection for underground service.

CNCJ (Zhejiang Chengjiu Pipeline Co., Ltd.) manufactures AWWA C207 steel flanges for water infrastructure projects worldwide. As a factory - not a trading company - we provide full material traceability, dimensional certification, and third-party inspection on request.
 

References & Sources

• AWWA C207: Steel Ring Flanges for Waterworks Service - 4 In. Through 144 In. (100 mm Through 3,600 mm). American Water Works Association. awwa.org
• AWWA C110: Ductile-Iron and Gray-Iron Fittings. American Water Works Association.
• AWWA C228: Stainless-Steel Pipe Flanges for Waterworks Service - Sizes 4 In. Through 144 In. American Water Works Association.
• ASME B16.5-2017: Pipe Flanges and Flanged Fittings NPS ½ Through NPS 24. American Society of Mechanical Engineers. asme.org
• ASME B16.47-2017: Large Diameter Steel Flanges NPS 26 Through NPS 60. American Society of Mechanical Engineers.