Class B Standard Steel Ring Flanges

AWWA C207 Class B steel ring flanges are the lightest-duty flanges in the AWWA waterworks standard, rated for a maximum working pressure of 86 psi. Ring flanges are flat steel plates with bolt holes and a center bore, designed to be welded directly to the pipe end without a hub or neck transition.

The simplicity of ring flange construction makes them the most economical option for large-diameter water mains where pressures are low and the pipe wall provides adequate reinforcement at the joint. Sizes range from NPS 4 through NPS 144, making them suitable for everything from service connections to major transmission mains.

Class B ring flanges are commonly used on gravity-fed water lines, reservoir outlets, and low-head pump discharge piping. The flat face design uses full-face gaskets that extend to the bolt holes, distributing the sealing load evenly across the joint. Bolt torque requirements are modest, and standard hand tools are sufficient for assembly at smaller sizes.