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fiberglass 36-inch Parshall flume manufactured by OpenchannelflowFiberglass (FRP / GRP) Parshall Flumes are the default material for most Parshall flume applications - from stream gauging to wastewater treatment plants.  

Fiberglass Advantages

Typically constructed of polyester resins, fiberglass Parshall flumes are light weight, corrosion resistant, economical, can have tight dimensional tolerances, and have considerable configuration flexibility.    

Light Weight

Fiberglass Parshall flumes are about 1/2 the weight of comparable steel construction flumes and are about the same weight as aluminum construction flumes. Their light weight makes fiberglass Parshall flumes particularly suitable for use in remote watershed / catchment monitoring applications where flume weight is an issue.

Corrosion Resistance

Polyester resins are suitable for most surface water, industrial discharge, and wastewater applications where the flow stream may be mildly acid or basic and at atmospheric temperatures.  For more aggressive / higher temperature applications, alternative resin systems (usually vinyl esters or epoxies) can be used, although it is usually more cost effective to use stainless steel construction.


With standard polyester construction, fiberglass Parshall flumes are an economical choice - priced between galvanized / painted steel and aluminum / stainless steel construction.

Dimensional Tolerances

The dimensional tolerances for fiberglass Parshall flumes are greatly dependent upon the dimensional accuracy of the molds from which they are produced.  For Openchannelflow fiberglass Parshall flumes, the following dimensional tolerances are typical:


  • 1/16-inch [1.59 mm] (12-inch or smaller Parshall flumes)

  • 3/32-inch [2.38 mm] (18-24-inch Parshall flumes)

  • 1/4-inch [6.3518 mm] (36-96-inch Parshall flumes)

  • 1/2-inch [12.7 mm] (120-144-inch Parshall flumes)

Other Flume Dimensions

  • 1/8-inch [3.18 mm] (24-inch or smaller Parshall flumes)
  • 1/2-inch [12.7 mm] (36-96-inch Parshall flumes)
  • 1-inch [25.4 mm] (120-144-inch Parshall flumes)

The above dimensions are within the +/-2% of nominal required by ASTM D1941-91(2013) Standard Test Method for Open Channel Flow Measurement of Water with the Parshall Flumes.

Configuration Flexibility

Openchannelflow fiberglass Parshall flumes are available with a wide selection of accessories and mounting / end configuration options.

More About Fiberglass (FRP) Parshall Flumes

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