AWWA Flanges

American Water Works Association C207 Steel Pipe Flange Standard

What Are AWWA Flanges?

AWWA (American Water Works Association) publishes standard C207, which covers steel pipe flanges for waterworks service. AWWA flanges are designed for lower pressures than ASME B16.5 flanges and are used primarily in water treatment plants, distribution systems, and municipal water infrastructure. They are typically larger diameter (up to 144") and lower pressure than ASME flanges.

AWWA C207 Flange Classes

  • Class B (86 psi) — Ring type
  • Class D (150 psi) — Ring type and Hub type
  • Class E (275 psi) — Hub type and Ring type
  • Class F (300 psi) — Ring type

The key distinction: Ring-type flanges are flat plates welded to pipe. Hub-type flanges have a forged or cast hub similar to weld neck flanges.

Ring Type vs Hub Type

Ring flanges are flat steel plates with bolt holes, welded to the end of the pipe. They are simpler and cheaper to manufacture. Hub flanges have a raised hub that provides additional strength at the pipe connection and are used for higher pressure classes. Hub flanges in AWWA are similar in concept to ASME weld neck flanges but with different dimensions.

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Available Sizes

AWWA C207 covers flanges from NPS 4 through NPS 144, much larger than ASME B16.5 (which stops at NPS 24). This makes AWWA the standard of choice for large-diameter water mains and transmission piping.

Common Materials

Carbon Steel plate (ASTM A36, A516-70) for ring flanges. Carbon Steel forgings (ASTM A105) for hub flanges. Flanges may be galvanized or coated for corrosion protection in buried or submerged applications.

AWWA vs ASME Flanges

AWWA flanges are for waterworks service at lower pressures. ASME flanges are for process piping at higher pressures. AWWA flanges come in larger sizes. Bolt patterns differ between the two standards. They are NOT interchangeable — an AWWA flange will not bolt up to an ASME flange of the same nominal size.

Related References