Standards Reference
AWWA C207 Plate-Cut Steel Flanges
AWWA C207 is where plate-cut steel flanges earned their reputation. The standard covers steel ring flanges and hub flanges from 4 inch through 144 inch in Class B, D, and E, and 4 inch through 48 inch in Class F, fabricated from rolled plate rather than forged from a billet. The four classes bracket the working pressure range from 86 psi cold water service up through 300 psi, and the same dimensional pattern that makes them drop-in compatible with ANSI B16.1 Class 125 cast iron is what keeps them in nearly every municipal waterworks, treatment plant, transmission main, and large diameter structural application across North America.
Why Plate-Cut, Not Forged
Forged flanges start as a heated steel billet that gets pressed or hammered into the rough flange shape and then machined to final dimension. That production path makes economic sense up through roughly 24 inches in standard ASME classes, where the forging die cost amortizes over thousands of identical parts.
At AWWA sizes, the calculus inverts. A 60 inch flange forged from a single billet would require press tonnage and a billet starting size that no economic forging operation supports. Plate-cut flanges side-step that problem by burning the ring profile out of ASTM A516 Grade 70 or A36 carbon steel plate, then machining the faces, drilling the bolt pattern, and welding on a hub where the design calls for one. The result is a flange that meets the same dimensional and pressure-temperature requirements at a fraction of the cost and lead time that any forging shop could quote at this scale.
The plate-cut production path also opens the door to non-standard dimensions. If a project needs a custom bolt pattern, a non-stock outside diameter, or an oversized inside diameter that no forging die supports, plate-cut is the only practical answer. We supply both standard AWWA C207 flanges from inventory and custom plate-cut work for cases that fall outside the published table.
AWWA C207 Pressure Classes
The standard organizes plate-cut steel flanges into four pressure classes. The class determines working pressure, plate thickness, and where the flange fits in the system. Class B, D, and E cover the full 4 inch through 144 inch range; Class F is published for 4 inch through 48 inch only.
| Class | Working Pressure | Typical Service | Bolt Pattern |
|---|---|---|---|
| Class B | 86 psi CWP | Buried municipal water, low head | Matches B16.1 Class 125 |
| Class D | 175 psi CWP | Treatment plants, transmission, pumps | Matches B16.1 Class 125 / B16.5 Cl 150 |
| Class E | 275 psi CWP | High pressure mains, pump discharge | Heavier pattern, see C207 table |
| Class F 4 in to 48 in only | 300 psi CWP | Hydroelectric, penstock, severe service | Heaviest C207 pattern |
Cold working pressure (CWP) ratings apply at 100 F. Higher temperatures derate per the C207 table. Confirm against the published standard for any service above ambient.
Large Diameter to 144 Inch
The size range is where AWWA C207 separates from the ASME world. B16.5 stops at 24 inch. B16.47 extends to 60 inch. AWWA C207 keeps going. The published table covers 4 inch through 144 inch in standard increments, and plate-cut fabrication makes anything in between available on a project basis.
A 96 inch AWWA Class D flange has an outside diameter of 122 inches, a bolt circle of 117 inches, and forty-four 1-1/2 inch bolt holes. A 144 inch Class D flange runs 173 inches outside, 166-1/2 inch bolt circle, and sixty-eight 1-3/4 inch bolt holes. These are not parts that ship out of a stock yard the way a 6 inch Class 150 weld neck does. They are made to order, frequently with project-specific facing, drilling, and hub details, and the production lead time runs in weeks rather than days.
For projects that already know the diameter and class but need confirmation on bolt circle, hole count, or thickness, our inside sales group can pull the C207 table value and confirm against current mill capability. Where the project diverges from the published table, we coordinate the custom plate-cut work with the partner mills we have used for that scope.
Drop-In Compatibility With Cast Iron
The single most useful feature of AWWA C207 Class B and Class D is that the bolt pattern matches ANSI B16.1 Class 125 cast iron in every size. Same outside diameter. Same bolt circle. Same bolt count. Same hole size. A retrofit project can pull an aging cast iron flange off a valve, pump, or manifold and bolt a new plate-cut steel flange to the existing mating part with the same studs and gasket.
That compatibility extends, in most sizes, to ANSI B16.5 Class 150 forged steel. A waterworks butterfly valve with AWWA Class D flanges will bolt to a Class 150 weld neck on the upstream side and a Class 125 cast iron tee on the downstream side, all using the same bolt and gasket spec. The pressure ratings differ, but the joint geometry does not.
The benefit on a retrofit is that the structural and piping footprint stays the same while the flange itself gains ductility, inspectability, and weight reduction. Cast iron at large diameter is heavy. A 36 inch Class 125 cast iron flange weighs over 400 pounds. The C207 Class D equivalent runs closer to 220 pounds, which changes hanger sizing, lift planning, and the structural load on the existing rack.
One caution on the cross-standard match. C207 is flat-face by design, and B16.1 Class 125 cast iron is flat-face, so the geometry works cleanly. If a project tries to extend the same idea to a forged raised-face flange against cast iron, the raised face concentrates bolt load on a small annular ring and can crack the cast iron during makeup. Use flat-face on the steel side any time the mating part is cast iron, regardless of standard.
Structural and Non-Pressure Applications
Plate-cut flanges in AWWA C207 dimensions show up in plenty of places that have nothing to do with water service. The combination of large diameter, flat face, and predictable bolt pattern makes them a default choice for structural columns, wind tower base plates, sign foundations, transmission line monopole bases, and any application where a circular bolted joint at scale is needed.
For these structural uses the flange is typically blank, meaning no bore drilled through the center, and the material may be A36 structural plate rather than the pressure-vessel grade A516-70 that C207 calls out by default. The bolt pattern still follows the C207 dimensional template because that table is the most commonly referenced source of large diameter bolt circles in North American engineering.
We supply both pressure-rated AWWA flanges with MTR documentation and structural blank flanges for non-pressure use. The drawings differ. The order documentation differs. The mill source differs. Confirm the application when you request the quote so we route the order to the right production path.
AWWA C228 Stainless Counterparts
For corrosive water, brackish service, or treated wastewater, the stainless equivalent is AWWA C228. The standard parallels C207 in dimension but specifies austenitic stainless plate, typically 304L or 316L, with the same Class B, D, E, F pressure rating structure.
316L is the more common spec on coastal raw water intakes, on reverse osmosis pretreatment, and on the chemical feed side of water treatment plants. 304L sees use where chlorides are not a factor. Both come from the same plate-cut production path as the carbon steel version, and the project documentation follows the same MTR and heat traceability rules.
Material and Documentation
Carbon steel AWWA C207 flanges come standard in ASTM A105 (forged hub variants), A516 Grade 70 (plate ring), and A36 (structural blank). Stainless C228 work uses A240 plate for the ring and A182 forgings where a hub is welded on. Specifying the plate grade matters: municipal and treatment plant contracts usually call out A516-70 by default; structural blank work commonly accepts A36; chemical service work often demands a specific A240 stainless grade with heat traceability.
MTRs are standard on any pressure-rated AWWA flange we supply. For buried municipal water work where Buy American Iron and Steel (AIS) provisions apply, melt origin documentation is available on request. For projects with BABA or ARRA exposure, confirm the requirement on the RFQ so the order routes to a qualifying mill.
Need a Plate-Cut Flange Quoted?
Call (281) 484-8325 or email sales@texasflange.com with the size, class, and any custom drilling or facing requirements. Standard sizes ship from inventory. Custom work runs against our partner mills.
Contact Us