Overview
AWWA C207 is the American Water Works Association standard for steel ring and blind flanges intended for water and wastewater service. It is designed to be a highly cost-effective, lighter alternative to ASME B16.5 for massive water pipelines operating at ambient temperatures and low pressures.
Scope & Applicability
Applies To Industries
Covers — waterworks steel flanges:
- Sizes from 4 in. through 144 in. (NPS 4 to 144).
- Classes B (86 psi), D (150-175 psi), E (275 psi), and F (300 psi).
- Hub (Slip-on) and Ring (Plate) type flanges.
Does NOT cover (exclusions) — the following are governed elsewhere:
- Process or hydrocarbon service → ASME B16.5 / B16.47.
- High temperature or steam service.
Key Requirements
AWWA C207 optimizes for low-pressure, ambient-temperature water:
- Material — allows the use of lower strength commercial quality steel plate to cut costs.
- Facing — all flanges are Flat Face (FF) to prevent damage to mating cast iron equipment (valves, pumps) common in waterworks.
Technical Details
The major advantage of AWWA C207 is cost and weight. An AWWA Class D ring flange is significantly thinner and cheaper than an ASME B16.5 Class 150 flange, yet perfectly adequate for municipal water pressures.
ASME Compatibility
AWWA C207 Class B, D, and E flanges match the bolt circle diameter and number of bolts of ASME B16.5 Class 150. AWWA Class F matches ASME Class 300. This allows a waterworks flange to bolt directly to standard ASME valves.
Engineering Notes
While AWWA Class D and ASME Class 150 have the same bolt hole pattern, the bolts used must be carefully selected. Because the AWWA flange is thinner, standard ASME bolt lengths will be too long and may not thread down far enough to clamp the gasket.
Source, Edition & Status
- Publisher
- AWWA
- Industries
- Waterworks, Municipal
- Last Reviewed
- 2026-07-01
- Last Updated
- 2026-07-01
- Verified By
- Engineering content reviewer
- Content Status
- reviewed