Flanges for US water and wastewater plants
Treatment plants, pump stations and transmission mains mix two flange families: AWWA flanges on the large water pipe and ASME flanges on the process and chemical piping inside the plant. Mixing them up is the most common flange mistake on these projects.
US water and wastewater projects use AWWA C207 steel flanges and AWWA C228 stainless flanges on large water pipe, and ASME B16.5 Class 150 flanges, often flat face to mate with cast and ductile iron pumps and valves, on the process, chemical and air piping in the plant. Stainless 304L and 316L is used where the water is aggressive, chlorinated or ozonated. We supply AWWA C207 and C228 flanges and ASME flanges in carbon and stainless steel, each heat with an EN 10204 3.1 mill test report.
Where flanges are used in water and wastewater
| System | Flange | Class and material |
|---|---|---|
| Raw and finished water mains | AWWA C207 slip-on ring or blind flanges | AWWA class to the line pressure, carbon steel |
| Stainless water piping | AWWA C228 flanges, or ASME B16.5 in 304L and 316L | Stainless |
| Pump stations and valve vaults | Flat face flanges at cast and ductile iron pumps and valves | ASME B16.5 Class 150 FF, A105 |
| Aeration and process air | Slip-on and plate flanges | Class 150, 304L or A105 |
| Chemical feed: hypochlorite, ferric, caustic | Weld neck or lap joint with stub end | 316L, duplex |
| Ozone and UV disinfection | Weld neck or slip-on | 316L |
AWWA and ASME flanges are not interchangeable
AWWA C207 flanges share bolt circles and bolt holes with ASME B16.5 Class 150 up to NPS 24 in most of their classes, but they are thinner and rated for water service at modest pressure only. Above NPS 24 the two families differ. A Class D AWWA flange, for example, is rated 175 psi up to NPS 12 and 150 psi above, while an ASME Class 150 flange in A105 is rated 285 psig at 100 °F. Order each line to the standard on the drawing, and check the mating valve or pump. Our AWWA vs ASME guide sets out the differences.
Flat face flanges at cast iron and ductile iron equipment
Pumps, valves and meters in water plants are often cast or ductile iron with flat face flanges. Bolting a raised face steel flange to them concentrates the bolt load on the raised ring and can crack the iron flange. Use a flat face flange and a full-face gasket at these joints.
Stainless steel for aggressive water
Chlorinated and ozonated water, brackish sources and chemical feed lines attack carbon steel. 304L is the usual choice for plant water piping and 316L, with 2 to 3% molybdenum, where chlorides are higher. Lap joint flanges with 316L stub ends keep the flange ring out of the water and cut the cost of large stainless lines. Duplex grades suit seawater intakes and desalination.
Ordering for a US project
Send your line list with the standard, type, size, class, bore or schedule, facing, material and quantity for each line, and we quote every line as specified. Every order ships from our works in Gujarat, India; we have no US office or warehouse. Each line is supplied to your line list, and ordering from India explains the documents, marking, packing and customs.
Frequently asked questions
Do you make AWWA flanges?
Yes, AWWA C207 steel flanges and AWWA C228 stainless flanges. Give the size, AWWA class and flange type on the line list and we quote each line as specified.
Will an ASME Class 150 flange bolt to an AWWA flange?
Up to NPS 24 the bolt circle and holes match for most AWWA classes, so they bolt up, but the joint takes the lower rating. Above NPS 24, check both drawings, as several sizes differ.
Can you supply plate flanges for low pressure air and water?
Yes. Plate (slip-on without hub) flanges in A105, A516 Grade 70 plate or stainless, drilled to ASME B16.5 Class 150.
Sources
- AWWA C207, Steel Pipe Flanges for Waterworks Service, Sizes 4 In. Through 144 In.
- AWWA C228, Stainless-Steel Pipe Flanges for Water Service, Sizes 2 In. Through 72 In.
- ASME B16.5, Pipe Flanges and Flanged Fittings, NPS 1/2 through NPS 24
- ASTM A182/A182M, Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service