Waterworks Industry Flanges

AWWA C207 Flanges for Water Treatment and Distribution Systems

Overview

Waterworks flanges follow AWWA C207 rather than ASME B16.5. These flanges are designed specifically for large-diameter, low-pressure water service found in municipal water treatment plants, distribution systems, and wastewater facilities. AWWA flanges are lighter and less expensive than their ASME counterparts because water service operates at significantly lower pressures.

AWWA C207 Classes

AWWA C207 defines four pressure classes, each available in ring type or hub type configurations. Ring flanges are flat plates welded to the pipe end, while hub flanges have a short raised hub that provides additional strength.

  • Class B — 86 psi — ring type flange for general low-pressure water service; the most common class for gravity-fed distribution
  • Class D — 150 psi — available in both hub and ring type; used for pump discharge and pressurized mains
  • Class E — 275 psi — available in both hub and ring type; specified for higher-pressure transmission mains and pump stations
  • Class F — 300 psi — ring type flange for the highest pressure waterworks applications

Common Applications

AWWA flanges are used throughout municipal water infrastructure for connections that need to be assembled and disassembled for maintenance.

  • Water treatment plant process piping and filter connections
  • Water distribution mains at valve and fitting connections
  • Pump station suction and discharge piping
  • Reservoir and tank inlet and outlet connections
  • Wastewater treatment plant piping and outfall lines

Size Range

AWWA C207 covers nominal pipe sizes from NPS 4 through NPS 144 (12 feet in diameter). This range far exceeds ASME B16.5, which only covers up to NPS 24, and ASME B16.47, which extends to NPS 60. The largest waterworks flanges are used on major transmission mains, intake structures, and large pump stations.

Coating and Lining

Waterworks flanges are frequently coated or lined to protect against corrosion in buried or submerged service. Common coating systems include:

  • Fusion bonded epoxy (FBE) — the most common modern coating for both interior and exterior surfaces
  • Coal tar enamel — a traditional exterior coating for buried flanges and fittings
  • Polyurethane — used for exterior coating where abrasion resistance is needed
  • Cement mortar lining — interior lining that provides both corrosion protection and a smooth flow surface

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Related References