Plate Flanges & Flat Face Flanges

If API flanges are built for the punishing requirements of oil and gas, AWWA flanges are for service on the other end of the demand spectrum: much less stress and corrosion. Designed by the American Water Works Association, these flanges are built for lower-pressure applications - think 300 psi or less - where temperatures are ambient and whatever's flowing through the pipe isn't going to eat the metal alive. Most of the time that means well water or wastewater, but they also show up in slurry lines and plant piping where pressure requirements are minimal.

The governing spec here is AWWA C207, which covers carbon steel rings and blinds. You'll typically see these in mild carbon steel or stainless, and they're almost always either a ring slip-on or blind disc style. No raised faces, no ring joints - just a flat face sealed with a rubber gasket. Simple, cost-effective, and they get the job done.

One thing worth knowing: AWWA flanges are increasingly being used in structural steel applications too, particularly when a project needs to mate or fill a gap between existing flanges. Their cost and weight profile makes them attractive for that kind of work.

On the dimensional side, C207 flanges are designed to play nice with other common standards. The OD and bolt pattern matches B16.1 Class 125, and they'll also line up with B16.5 Class 150 up to 24" and B16.47 Series A up to 60" NPS, although AWWA is available at even larger sizes. The main difference you'll notice is thickness, and the absence of a raised face or hub (unless you're dealing with a legacy system).

Material-wise, AWWA is a bit more flexible than ASME. C207 allows grades like A36, A516-70, A181-60, and A105 - all commercially abundant and easy to source - because the minimum yield and tensile requirements (32 ksi and 50 ksi) aren't as demanding. Many options are available as import stock, and domestic can be provided as well for USA government funded and municipal infrastructure related projects.