At API International, we produce stainless steel pipe flanges specifically for waterworks service, ensuring compliance with AWWA C228 specifications. Our inventory includes blind and slip-on flanges designed to provide superior corrosion resistance and reliable sealing in municipal and industrial water systems. We offer a comprehensive range of dimensions in both domestic (AIS) and import materials, supported by our capability to provide custom-machined solutions for unique or specialized project requirements.
AWWA C228 is the modern standard governing stainless steel pipe flanges for water service, providing rigorous guidelines for design, materials, and dimensions in both potable and non-potable systems. By utilizing high-grade, corrosion-resistant alloys—primarily 304/304L and 316/316L—these flanges offer superior durability in chemically aggressive, high-salinity, or high-humidity environments. This makes AWWA C228 flanges the preferred specification for critical infrastructure such as desalination plants, wastewater treatment facilities, and marine applications where long-term material integrity is paramount.
The AWWA C228 standard covers stainless steel ring and blind flanges in sizes ranging from 2″ to 72″. Engineered for durability, these flanges are the preferred choice for corrosive, high-humidity, or chemically aggressive environments. While they maintain pressure ratings similar to their AWWA C207 carbon steel counterparts, they are uniquely designated with an ‘S’ prefix (e.g., Class SD or SE) to explicitly denote their stainless or alloy composition.
| 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 |
A Slip On Flange is a type of pipe flange that is slipped over the end of a pipe and welded in place.
A Blind Flange is a detachable sealing device used to block off a pipeline or to create a stop.
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 typically used in municipal pipelines, treatment plants, irrigation systems, and other applications up to 300 psi.
The American Water Works Association (AWWA) provides two main standards for flanges for water-work applications:
AWWA C207 – carbon steel flanges
AWWA C228 – stainless steel flanges
These standards also define dimensions, drilling patterns, pressure ratings, and material properties.
AWWA C207 covers carbon steel flanges, while AWWA C228 covers stainless steel flanges for the same applications. Both define dimensions, pressure classes, and material requirements.
These ratings apply to water service and depend on flange size and material.
API International stocks AWWA C228 flanges across multiple nominal pipe sizes, pressure classes, and material options to meet your project requirements. Our machine shop can also modify stock products to accommodate any special project requirements. Contact API International’s experienced sales team, and we will help you select the right flange for your application.
• Custom Bolt Holes, Overbore, Counterbore, Tapped, Welds, O-ring Grooves, Threads, Special Serrations, Bevels, Chamfers
• Metric Parallel, Metric Tapered, Parallel (BSPP), Taper Thread (BSPT), UN/UNF/UNC Thread, NPT (National Pipe Thread)
• MWD
• Contact API’s engineering department for exact specifications and tolerances.
Plastic: Delrin, POM, Lexan, Nylon 66, Nylon 6, PEEK, PP, PE, Acetal
Rubber: EPDM, Neoprene, Buna-N, Viton
Aluminum: A2011, A2024, A2017, A5052, A5056, A6061, A6063, A6463, A6082, A7075
Copper: 3600, 3604, 3771
Titanium: 1-28
Steel Series:
• Ductile Iron: ASTM A536
• Carbon/Mild Steel: A105, A36, A516-70, A572-50, etc.
• Stainless Steel:
- 300 Series – 303, 304, 304L, 316, 316L
- 400 Series – 420J2, 430, 434, 442
Special Metals: Hastelloy, Inconel, Incoloy, Duplex 2205, Super Duplex 2507, Chrome Steel, alloys, or their equivalents
Stock Finish, Spiral Serrated (Phonographic), Concentric Serrated, Smooth Finish, Cold Water Finish, MWD, Phonographic
Dipped, Nickel Plating, Zinc Plating (clear, yellow, black, red, blue), Super Agitine, Powder, Painted, Galvanized, Epoxy, Lacquer
Water/Wastewater, Irrigation, Agriculture, HVAC, Marine, Exhaust, Mining, Energy/Power Generation/Oil
• Forged:
- Ring Rolling:
• Materials: Carbon Steel, Stainless Steel, Duplex
• Size: 2–202”
• Cast:
- Centrifugal Casting (Industrial):
• Material: Stainless Steel
- Continuous Casting:
• Stainless Steel
- Sand Casting:
• Material: A536, Stainless Steel, Ductile Iron
- Investment/Lost-Wax/Precision Casting
• Stainless Steel
Machining: Milling, Turning, Facing, Boring, Drilling, Tapping, Counter Sinking, Laser Cutting, Water Jet, Plasma Cutting
Products | Type | Materials | Size Range |
|---|---|---|---|
Flanges | Flat-Face, Raised-Face, & Plate: Slip-On/Ring Weld, Neck, Blind, Socket Weld, Orifice, Reducing, Threaded | See Materials List | 5–202″ |
Gaskets | Molded, Extruded, sheet | EPDM, Buna-N, NBR, Non-Asbestos (GNA), Red Rubber (GRR), Viton | 5–60″ |
Screens For Filters | Basket Screens and Cone Screens (Perforated, Mesh) | Galv. Carbon Steel, Carbon Steel, Stainless Steel | 6”D x 8’-H |
Rings | Exhaust Rings (Marmon Flanges for DPF Filters) | Carbon Steel, Stainless Steel, Aluminum | 1–16” |
Seamless Rolled Rings | Forged | Carbon Steel, Stainless Steel, Aluminum | 1–165” |
Square Hole Rings | Repair Couplers | Stainless Steel, Carbon Steel, Galvanized, Epoxy Coated | 3–32” |
Fabricated Assemblies | Weldments, Pipe Spools, Valve Bodies, Silencer Housings | Carbon Steel, Stainless Steel | 2–24” |
Long/Short Radius Elbows | EN 10253-2–S235, P235GH–P265GH–P265NL and ASTM A234, WPB, WPC/ A420 WPL6, WPL3/ A860 WPHY52/ ASTM A234 WP11, WP22, WP5, WP9–16Mo3 | 304L & 316L Stainless Steel | (45° & 90°): OD: 21.3mm (1/2”)–3048mm (120”) WT: Up to SCH. XXS/160 |
Miscellaneous | Tubesheets / Diffuser Plates / Baffles / Ferrules / Sleeves / Pins | Carbon Steel, Stainless Steel, Duplex | 5–104” |
Who we are
API International is a manufacturer and wholesale distributor of flanges, expansion joints, valves, other pipe fittings and custom fabricated parts. We offer a wide variety of AIS & imported flanges along with other industrial pipe fitting and accessories. Customers turn to us when they need quick delivery of parts and are looking for a higher level of customer service. Standard parts are stocked in one of our conveniently located warehouses for quick distribution throughout the United States.
