AWWA C207 Flange Classes B, D, E and F: Pressure Ratings and Selection Guide
AWWA C207 is the American Water Works Association standard for steel pipe flanges for waterworks service. It covers sizes from 4 in. (100 mm) to 144 in. (3,600 mm).
Compared with ASME flanges designed for oil, gas and process piping, AWWA C207 flanges are rated for lower pressures and are lighter. On large-diameter water transmission lines this saves both steel and cost.
Classes and pressure ratings
| Class | Size range | Working pressure | Approx. bar | Typical use |
|---|---|---|---|---|
| B | 4"–144" | 86 psi | 5.9 bar | Low-pressure lines, treatment plant piping |
| D | 4"–12" | 175 psi | 12.1 bar | Municipal distribution, water plants |
| D | 14"–144" | 150 psi | 10.3 bar | Large-diameter transmission mains |
| E | 4"–144" | 275 psi | 19.0 bar | High-pressure transmission, pump stations |
| F | 4"–48" | 300 psi | 20.7 bar | Critical, high-pressure lines |
Flange thickness and weight increase with the class letter. Note that the Class D rating drops for sizes of 14 in. and above.
The values above are the working pressures permitted for each class. Hydrostatic test pressure and surge (water hammer) allowance must be checked separately against the project specification.
Flange types: ring, hub and blind
Ring flange
Slipped over the pipe and fillet-welded inside and outside. It is the most common and most economical type for large diameters. Yazıcı Endüstri manufactures ring flanges from 4" to 144".
Hub flange
The hub reduces stress at the weld and gives higher strength. Manufactured from 4" to 96".
Blind flange
Used to close the end of a line. Manufactured from 4" to 72". For very large diameters, a dished head is usually preferred over a flat blind flange.
AWWA C207 vs ASME B16.5 / B16.47
| AWWA C207 | ASME B16.5 / B16.47 | |
|---|---|---|
| Service | Water and wastewater | Oil, gas, process, steam |
| Sizes | 4"–144" | B16.5: 1/2"–24", B16.47: 26"–60" |
| Pressure | Up to 300 psi | Class 150–2500 |
| Facing | Usually flat face (FF) | Usually raised face (RF) |
| Material | Carbon steel (e.g. ASTM A36, A105) | Carbon, alloy and stainless steel |
| Weight | Lighter | Heavier |
In some sizes the AWWA C207 bolt pattern matches ASME Class 150, which is why the two are often confused at valve and pump connections. Thickness and pressure ratings differ, however, so bolt-pattern compatibility should be checked against the dimension tables for each size.
Gaskets and bolting
Because AWWA flanges are flat-faced, they are normally used with full-face or ring-type rubber gaskets (EPDM, SBR). Spiral-wound gaskets are intended for ASME raised-face flanges and are generally not needed on AWWA flanges. Bolt grade is selected per the project specification.
How to choose the right class
- Determine the maximum working pressure of the line and the surge allowance.
- Choose the lowest class that meets that pressure. An unnecessarily high class adds weight and cost.
- Check the bolt pattern of the valve, pump or existing line to be connected.
- Choose ring or hub type based on pipe wall thickness and loading.
- Specify the coating (painted, galvanized) and material certificate (EN 10204 3.1) requirements.
AWWA C207 flange manufacturing at Yazıcı Endüstri
Yazıcı Endüstri has manufactured flanges and pipe fittings in Istanbul since 1998 and exports to more than 37 countries. Large-diameter AWWA flanges are plasma cut and CNC machined at our Esenyurt, Istanbul plant, in sizes up to DN 3000. See also custom and large-diameter flanges.
Frequently asked questions
What is the pressure rating of an AWWA C207 Class D flange?
175 psi (about 12 bar) for 4"–12" and 150 psi (about 10 bar) for 14" and larger.
Can an AWWA flange be bolted to an EN 1092-1 PN10 flange?
Usually not. The bolt patterns differ. An adaptor or a custom-drilled flange is needed.
Which AWWA standard covers stainless steel flanges?
Stainless steel flanges for waterworks service are covered by AWWA C228.