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Openchannelflow Flume Metering Manholes take our proven open channel flumes and adapts them to measure below grade flows.  

Openchannelflow - dig it - drop it - done - fiberglass manhole slogan

Flume Metering Manholes are easy to install, require minimal line downtime, and are factory integrated.  All fiberglass construction means that Openchannelflow Flume Metering Manholes are more than a match for all but the most aggressive of flows. The result is a manhole that is a watertight and corrosion resistant structure from which operators can accurately (and safely) measure and sample flows.

Flume Integration

Flumes available for integration:

Strength Built In

At the core of each Openchannelflow Packaged Metering 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 flume sized to accurately measure the flow!

Metering Manhole Advantages

Flume Metering Manholes provide:

  • Single source responsibility
  • Confidence the flume in installed correctly
  • Properly formed inlet / outlet transitions
  • An ability to integrate a wide range of flume styles and sizes
  • Virtually no maintenance
  • Minimal downtime (perfect for installation during plant shutdowns)
  • A safe environment in which an operator can measure and sample flow

ASTM D3753 Compliance

Unlike competing Flume Metering Manholes which claim to meet ASTM D3753, the interior of Openchannelflow Packaged Metering Manholes are pigment / gel coat free – allowing for visual inspection and quality control of the tube during and after production and meeting D3753.


A variety of top styles are available with Openchannelflow Flume Metering Manholes, including:

Openchannelflow Flume Metering 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].

Flume metering manhole components

  • Cover 

  • OSHA-complaint fiberglass ladder

  • Thru-wall coupling

  • Integral base / mounting flange

  • Flume

  • Inlet / outlet piping

Many of the accessories Openchannelflow has developed for our flumes and Packaged Metering Manholes can be integrated into our Flume Meter Manholes:

As with any flume application, the flow must be sub-critical and non-full pipe.

More About Flume Manholes

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