Two of the most referenced standards in the flange industry are AWWA C207 and AWWA C228. While they can look similar at first glance, they are engineered for very different environments and material performance. AWWA C207 flanges are typically used in clean water systems and general infrastructure due to their strength and cost-effectiveness, while AWWA C228 flanges are designed for corrosive environments, offering long-term resistance against rust, chemicals, and extreme temperatures. In this guide we will discuss the major differences between AWWA C207 and C228 flange standards and also learn how to select the right type for your specific project.
Brief Overview of AWWA C207 and C228 Flanges
AWWA C207
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, pump stations, and other infrastructure projects.
AWWA C228
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. These flanges are manufactured using corrosion-resistant stainless steel alloys, which enhances their performance in chemically aggressive or humid conditions. AWWA C228 flanges are ideal for applications like desalination, wastewater treatment, or marine infrastructure.
Comparison Table: AWWA C207 vs. C228
| Characteristic | AWWA C207 | AWWA C228 | Engineering Note / Balance Point |
|---|---|---|---|
Material Composition | Carbon steel (typically ASTM A36 or A283 Grade C) | Stainless steel (typically ASTM A240, 304/304L, 316/316L, or duplex alloys) | C207 offers high strength but poor corrosion resistance; C228 is engineered for superior corrosion resistance in harsh environments. |
| Corrosion Resistance | Low – prone to rust in humid, saline, or chemical environments | High – resists corrosion in water, salt spray, and many chemical environments | Use C207 in non-corrosive conditions; use C228 in systems exposed to chemicals, saltwater, or high moisture. |
| Pressure Ratings (Class) | Class B (86 psi), Class D (175 psi), Class E (275 psi), Class F (300+ psi) for sizes 4″-144″ | Varies by flange design and alloy; typically designed to meet/exceed Class D/E ratings under corrosive load | Both offer strong pressure ratings, but C228 is preferred for systems where degradation over time from corrosion could impact pressure performance. |
| Design Standard | ANSI/AWWA C207 – Steel pipe flanges for waterworks service from 4″ to 144″ NPS | ANSI/AWWA C228 – Stainless steel flanges for corrosive environments, same dimensional tolerances | Dimensional compatibility is maintained between both; ensures easy substitution in designs. |
| Durability in Neutral Environments | High – performs well in clean water, municipal, or indoor systems | Very high – over-engineered for durability even in neutral environments | In clean municipal settings, C207 lasts decades; however, if unexpected moisture exposure occurs, C228 offers safer long-term protection. |
| Durability in Corrosive Environments | Low – subject to pitting, oxidation, or material loss over time | High – resistant to acids, chlorides, and extreme temps depending on alloy | C228 minimizes maintenance and safety concerns in harsh systems. |
| Common Applications | Water treatment, building water systems, clean water transmission, general piping | Desalination, chemical plants, wastewater, marine systems, food-grade systems | C207 dominates in budget-driven municipal systems; C228 is best in coastal, industrial, or regulated environments. |
| Lifespan (typical) | 15–25 years in clean environments | 25–50+ years in corrosive or marine conditions | When used in correct environment, C207 is cost-effective; when exposed to corrosion, C228 is far more reliable and economical over time. |
| Initial Material Cost | ~$0.75–$1.20 per lb for carbon steel | ~$2.00–$4.00 per lb for stainless steel depending on grade | C228 flanges are 2x–4x more expensive upfront; project engineers must weigh long-term risk and ROI. |
| Lifecycle Maintenance Cost | Higher – potential for inspection, repainting, or replacement if corrosion sets in | Lower – minimal maintenance needed | For buried, submerged, or exposed flanges, lifecycle savings of C228 can outweigh upfront cost. |
| Weldability & Fabrication | Easier to weld and machine using standard carbon steel tools | Requires special tooling and higher expertise for welding/fabrication | Consider shop readiness and installation complexity: C207 is simpler; C228 demands skill. |
| Weight (Density Impact) | Slightly heavier – carbon steel ~7.85 g/cm³ | Slightly lighter or similar – stainless steel ~7.9 g/cm³ (duplex may be lighter) | Overall negligible weight difference unless handling large-scale units; not a deciding factor. |
| Standards Compliance | Compliant with ANSI/AWWA C207-18 | Compliant with ANSI/AWWA C228-22 | Both meet AWWA dimensional specs; choose based on material performance needs. |
How to Choose the Right Flange for Your Project
1. Understand Your Project Requirements
Start by clearly defining the media your pipeline will carry and the conditions it will face. If your system handles clean water or air and operates in a controlled environment, AWWA C207 carbon steel flanges usually work. But, if the system involves corrosive chemicals, high humidity, or salt exposure, then stainless steel C228 flanges are the more suitable choice.
2. Match the Flange to Environmental Conditions
Keep in mind that flange performance will be heavily impacted by the surrounding environment. C207 flanges are strong but vulnerable to corrosion if left uncoated or exposed to moisture. C228 flanges are made from stainless steel or corrosion-resistant alloys, which makes them ideal for marine, chemical, or outdoor applications.
3. Consider Pressure and Temperature Limits
Both C207 and C228 flanges are manufactured to AWWA standards and can handle typical municipal and industrial pressure ratings. However, C228 flanges offer greater long-term performance in systems with extreme temperature fluctuations or thermal cycling, where material fatigue or seal degradation can become issues over time.
4. Evaluate Long-Term Durability
In clean or dry systems, carbon steel flanges can last 15–25 years with basic maintenance. But in corrosive conditions, their lifespan goes down significantly. On the other hand, stainless steel C228 flanges offer 30–50 years of service with minimal maintenance, which makes them a better fit for systems where access is limited or shutdowns are costly.
5. Balance Initial Cost and Lifecycle Value
C207 flanges are more affordable upfront and widely used for budget-sensitive projects. But it is necessary to keep in mind that they often come with higher maintenance and earlier replacement costs. While C228 flanges require a larger initial investment, they offer longer service life, lower maintenance, and better resistance to failure.
6. Ensure Standards and Availability
Both flange types meet AWWA specifications, but material choice can affect procurement timelines. Stainless steel flanges may have longer lead times due to alloy availability or fabrication processes. If your project has tight deadlines, consider material availability when placing your order and choose a supplier with proven AWWA compliance and mill certification.
7. Final Decision Guidelines
| Project Environment | Recommended Flange |
|---|---|
| Clean water, low cost | AWWA C207 |
| Chlorinated, acidic, or saline systems | AWWA C228 |
| High vibration or thermal cycling | AWWA C228 |
| Indoors, dry mechanical rooms | AWWA C207 |
| Marine, wastewater, or chemical plants | AWWA C228 |
Summary and Support:
Selecting between AWWA C207 and C228 flanges involves more than just comparing material costs. It requires a clear understanding of environmental conditions, pressure demands, and long-term system performance. C207 flanges, made from carbon steel, are a reliable and economical choice for clean water and non-corrosive environments. C228 flanges, made from stainless or alloy steel, provide superior corrosion resistance and durability for more demanding, high-risk applications. By considering such factors as: the fluid type, site conditions, and lifecycle costs, you can make an informed, cost-effective decision that supports system safety and longevity.
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
