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Weir Manholes occupy a unique place in Openchannelflow's manhole lineup.  While Flume Metering Manholes usually can cover flow rates more effectively, there are times when the special attributes of a weir are called for.  

Weir Manholes take our Weir Channels and integrate them into our fiberglass manholes.  Factory integrated and easy to install, Openchannelflow Weir Manholes allow drop-in place ease at a cost effective price.  Dig it!  Drop it!  Done!

Weir Manholes are most commonly used to measure dam seepage flows (where the collection of sediments is important), but they can also be used to measure flow on clean industrial and municipal discharges.

Keep in mind, as with any weir application, the flow must be sub-critical and non-full pipe entering the manhole.

Strength Built In

At the core of each Openchannelflow Fiberglass Weir Manhole is our fiberglass manhole tube.  While manhole configurations may differ, all Openchannelflow manhole tubes are designed to meet or exceed both ASTM D3753 and AASHTO H-20 standards.  The interior of these tubes is smooth and corrosion resistant.  The light tan coloration of the tube helps to maximize visibility inside the manhole.

To the barrel that we add a cover, base, mounting flange, and, most importantly, a weir sized to accurately measure the flow!

Weir Manhole Advantages

  • Accurate low flow measurement
  • Solids capture
  • Single source responsibility
  • Virtually no maintenance
  • Minimal downtime 
  • A safe environment in which to measure flow


  • Cover 

  • OSHA-complaint fiberglass ladder

  • Thru-wall coupling

  • Integral base / mounting flange

  • Weir channel

  • Non-slip fiberglass bench

  • Replaceable weir plate

  • Inlet / outlet piping


Openchannelflow Weir Manholes can be configured to your site needs, with a variety of top styles available:

Weir Manholes are available in diameters from 48 to 96-inches [1.22 to 2.44 m] and in depths up to 35-feet [10.7 m].

To complete the customization a range of manhole and flow accessories are available:

More About Weir Manholes

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