What Are AWWA Flanges? A Guide for Waterworks Projects

What Are AWWA Flanges?

An AWWA flange is a type of pipe flange designed for waterworks service. It follows standards developed by the American Water Works Association and is specifically intended for low-pressure water applications. AWWA flanges are governed by standards such as C207 and C228, which guide the design, manufacturing, and application of flanges used in water systems.

Main Features of AWWA Flanges

FeatureDetails
StandardsAWWA C207 (carbon steel), AWWA C228 (stainless steel)
Pressure RatingsFrom Class A (up to 50 psi) to Class F (up to 300 psi)
SizesTypically available from 2″-144″
MaterialsCarbon steel, ductile iron, stainless steel
TypesSlip-on-ring (2″-144″), blind (4″72″), hub ring (4″-96″)
ApplicationsWaterworks piping systems, irrigation, fire protection

Two AWWA Standards for Flanges

The American Water Works Association provides two official flange standards for water utility systems: AWWA C207 and AWWA C228. These standards define critical properties such as: bolt patterns and drilling specs, flange thickness, pressure classifications, acceptable material grades.
The Difference Between AWWA C207 and C228:
AWWA C207 is a standard for steel ring flanges for waterworks service, providing guidelines for the design, materials, dimensions, and testing of flanges used in water systems. The C207 standard includes several classes of flanges, each designed to handle different pressure ratings. These flanges are typically made from carbon steel and are designed to handle pressure requirements of waterworks systems in industrial applications. They are commonly used in pipelines, water treatment plants, and other infrastructure projects.
AWWA C228 is a newer standard that specifies stainless-steel pipe flanges for water service. It includes guidelines for the design, material, dimensions, and testing of stainless-steel flanges used in potable and non-potable water systems. Stainless steel offers enhanced corrosion resistance, making C228 flanges suitable for environments where water quality and longevity are critical.

Example Specifications for AWWA C207 and C228 Flanges:

SpecificationAWWA C207AWWA C228
MaterialSteel material conforms to the requirements of AWWA C207 specifications.Dual grade 304/304L & 316/316L stainless steel material conforms to the requirements of AWWA C228 specifications.
DimensionsThe flange thickness and bolt circle diameters vary according to pipe size, following specific tables in the standard.Conforms to the same dimensional criteria as the C207 standard, ensuring compatibility with existing systems.
Pressure ClassesA, B, D, E, FVarious classes are defined in the standard, similar to C207.
Use CaseStandard waterworks systemsCorrosive environments, potable water
Corrosion ResistanceRequires protective coatingHigh resistance, no coating needed
AvailabilityCommon for large-diameter pipingIdeal for treatment plants and coastal use
DesignRing-type flange suitable for slip-on or weld-neck connection.These can be slip-on, weld-neck, or blind types, depending on application requirements.

AWWA Flange Pressure Classes

AWWA flanges are classified based on their pressure ratings and strength.
Flange ClassMax Pressure (psi)Use Case
Class AUp to 50 psi (3.5 bar)Low-pressure systems, limited-duty use
Class BUp to 86 psi (6 bar)Light-duty water distribution lines
Class DUp to 175 psi (12 bar)Standard municipal water systems
Class EUp to 275 psi (19 bar)High-flow or elevated pressure zones
Class FUp to 300 psi (21 bar)Extra-duty or critical water lines

Where AWWA Flanges Are Used

Due to their large size availability and affordability, AWWA flanges are ideal for:

  • Water Treatment Plants

  • Water Distribution Systems

  • Sewage and Wastewater Systems

  • Irrigation Systems

  • Pump Stations

  • Stormwater Systems

  • Water Distribution Systems

  • Stormwater Systems

AWWA vs. ANSI/ASME Flanges

While AWWA flanges (both C207 and C228) are specifically designed for waterworks applications, ANSI flanges cater to a broader range of industries, including oil and gas, chemical, and power generation. Here are some key differences:
FeatureAWWA FlangeANSI/ASME Flange
ApplicationsWaterworks, utility pipingIndustrial, chemical, high-temp/pressure
Pressure RangeUp to 300 psiUp to 6170 psi or more (per ASME B16.5 Class 2500)
StandardsAWWA C207, C228ASME B16.5, B16.47
Size Range4″ to 144″½” to 24″ (larger via B16.47 Series B)
MaterialCarbon steel and stainless steelStainless steel, alloy, exotic metals
CostLower—ideal for large systemsHigher—engineered for specific tolerances
Read more about the differences between AWWA and ANSI flanges in our blog.

Why Choose AWWA Flanges?

For engineers, contractors, and utility providers, AWWA flanges deliver:

  • Affordable, large-diameter options

  • Proven long-term performance in water systems

  • Compatibility with multiple pipe sizes and fittings

  • Compliance with trusted AWWA engineering standards

Final Thoughts

If your project involves municipal water distribution, irrigation, or non-critical wastewater piping, AWWA flanges are a smart and reliable choice. Designed for low-pressure environments and backed by over a century of AWWA engineering, they continue to be the go-to solution for waterworks infrastructure across North America.
Our sales team at API can answer any questions about your flange requirements. Depending on its application, they can also recommend alternative products that may be better suited for your system. We also provide custom flange solutions tailored to your project specifications. Get connected with a dedicated sales representative today! Or call us: 503.692.3800
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