About Pressure Classes
Material type (carbon vs. stainless steel)
Flange dimensions
Operating temperature
Bolt pattern and gasket sealing surface
AWWA C207 Flange Pressure Classes (Carbon Steel)
AWWA C207 covers steel ring and blind flanges ranging from 4” to 144”. These flanges are categorized into four pressure classes, each designed for a specific pressure range and application environment. The materials conform to the requirements of AWWA C207 specifications but are typically ASTM A36 or A105 Grade C carbon steel. For blind flanges, AWWA recommends the use of Dish Assemblies for sizes above 48″.
| Class | Pressure Rating | Typical Sizes | Use Case / Notes |
|---|---|---|---|
| Class B | 86 psi | 4” to 144” | Low-pressure pipelines, treatment plants |
| Class D | 175 psi (1″–12″), 150 psi (14″–144″) | 4” to 144” | Mid-pressure municipal lines, water plants |
| Class E | 275 psi | 4” to 144” | High-pressure transmission, pump stations |
| Class F | 300 psi | 4” to 48” | Extreme pressure systems, critical infrastructure |
Example Applications:
Class B: Small facility connections
Class D: Municipal water mains
Class E: Long-distance water transfer pipelines
Class F: High-pressure industrial environments
AWWA C228 Flange Pressure Classes (Stainless Steel)
AWWA C228 standard covers stainless steel ring and blind flanges ranging from 2″ to 72″ (smaller sizes available when compared to C207). They are favored in corrosive, high-humidity, or chemical-laden environments. These flanges follow similar pressure classes but are designated with an “S” prefix to indicate stainless/alloy flange material. For blind flanges, AWWA recommends the use of Dish Assemblies for sizes above 48″. The materials conform to the requirements of AWWA C228 specifications but are typically 304L/316L Stainless Steel.
Example Applications:
Class SA: Groundwater systems, short-range potable pipelines
Class SB: Chlorinated water or municipal branches
Class SD: Desalination, water reuse, or UV disinfection systems
Class SE/SF: Chemical processing, marine intakes, high-salinity transfer lines
How to Select the Right Pressure Class
| Class | Pressure Rating | Typical Sizes | Ideal Environments |
|---|---|---|---|
| Class SA | 50 psi | 2″ to 14″ | Low-pressure, clean water |
| Class SB | 86 psi | 2″ to 60″ | Water distribution, general use |
| Class SD | 175 psi (1″–12″), 150 psi (14″–144″) | 2″ to 60″ | Treated water, wastewater |
| Class SE | 275 psi | 2″ to 72″ | Industrial water loops, tank connections |
| Class SF | 300 psi | 4″ to 48″ | Marine, chemical, high-pressure zones |
| Factor | Why It Matters |
|---|---|
| Operating Pressure | Select a class rated above your system’s maximum pressure |
| System Size | Larger diameters (above 14″) may have slightly lower pressure ratings for Class D |
| Media Type | Clean water, wastewater, chemical, or seawater all affect material and class selection |
| Environment | Outdoor, buried, marine, or corrosive settings may require stainless steel (C228) |
| Maintenance Access | Remote or hard-to-access flanges should favor longer-lasting, corrosion-resistant options (e.g., Class SE or SF) |
AWWA Flange Pressure Class Summary
| Standard | Material | Class Options | Max Pressure |
|---|---|---|---|
| AWWA C207 | Carbon steel | B, D, E, F | 86 to 300 psi |
| AWWA C228 | Stainless steel | SA, SB, SD, SE, SF | 50 to 300 psi |
