Fiberglass Flumes for Flow Measurement

Flumes are specially designed static structures or fittings that restrict the flow of fluid by narrowing the available passage area within a system. These simple components measure and monitor the flow of fluid in free-flowing conditions. The flume can accelerate flow rate through changes in its elevation, the shape of the floor, and the narrowing of system sidewalls, which can transform a subcritical flow of fluid to a critical or even supercritical flow that operators can easily measure. With a variety of standard and custom flume types available, industries can choose the type that best fits their application.

fiberglass parshall flumes


Advantages of Fiberglass Flumes

Selecting the right flume for an application’s environment, flow rate, and channel type allow that application to capitalize on the key benefits of using flow measurement flumes. These include:

  •     Control over fluid flow rate with high- and low-rate capabilities
  •     Versatility, as they come in various sizes and shapes
  •     Less head loss and easier debris passage in the stream of fluid compared to weirs
  •     Accuracy in making flow predictions
  •     Few maintenance requirements due to self-cleaning
  •     Easy installation with a compact footprint
  •     Readily available, including installation components



Fiberglass flumes give the flume more structural integrity and easy maintenance characteristics across diverse operating conditions and fluid types. The resin and glass fiber construction gives fiberglass some unique advantages for flume composition, including the versatility and malleability of the material. Fiberglass flumes also come in a wide range of shapes and colors for different operations. Properties of fiberglass that make it an excellent choice for flumes include:

  •     Mechanical strength, despite its lightweight
  •     Cost-effectiveness
  •     Resistance to corrosion from chlorine and other chemicals or contaminants
  •     Thermal, electrical, flame, pest, and microbe resistance 
  •     Ability to resist UV radiation damage with a gel coating


Flume vs. Weir

Both flumes and weirs control the open channel flow of fluid through a designated pathway. However, the way in which they guide and manage fluid flow is very different. Fluid passes through a flume, and fluid passes over the top of a weir. That dissimilarity in weir construction can introduce inertia in the fluid, reducing its head to approximately a quarter of that retained by a flume installation. Weirs have a dam plate that allows liquid pooling and results in lost force, as well as more frequent maintenance. Flumes, on the other hand, guide fluid and increase the force of its flow without significant head loss or lost potential. Flumes offer a better solution for moving fluid through a flat or low-gradient system of channels and ditches.


Types of Flumes

Learning about each flume type’s capabilities, advantages, and disadvantages will help to source the best flume for your flow measurement needs.

Palmer Bowlus Flumes
  • Palmer Bowlus Flumes : A Palmer-Bowlus flume’s u-shaped cross-section and long throat make it easy to install in pipes or u-shaped channels with long, straight runs. The Palmer-Bowlus flume offers an ideal measurement solution for mid-to-high flow rates, but measurements become less accurate if the flow depth becomes too low in comparison to the length of the flume itself. In environments with lower flow rates and higher solid content, sediment from the flow may settle upstream from the flume and cause flow issues.
    Some of the most frequent measurement applications for Palmer-Bowlus flumes include pipelines, manholes, sanitary sewers, and industrial runoff.
Parshall Flumes
  • Parshall Flumes: Parshall flumes offer an ideal solution for fixed-flow monitoring installations. As one of the most widely used flumes, Parshall flumes feature an open channel flow section that works well for measuring flow in installations such as canals and ditches. Even if flow spills off the end of the Parshall flume, users can still get accurate flow measurements as long as the discharge remains lower than the inlet.
    The applications for this type of flume are nearly universal because of its highly standardized nature. The Parshall flume is available in a variety of throat widths that conform to standard dimensions put forth by the U.S. Department of Interior’s Bureau of Reclamation. Common applications for Parshall flumes include wastewater treatment and municipal sewers.
Trapezoidal Flumes
  • Trapezoidal Flumes :Trapezoidal flumes offer an ideal measurement solution for flows with significant debris or solid content. Named for its trapezoidal cross-section, this flume also has a flat bottom that makes it easy to fit into most standard irrigation channels. As a result, measuring flow rates in irrigation ditches and channels is the most common application for trapezoidal flumes. Measurements remain accurate at high or low flow rates.
H/HS Flumes
  • H/HS Flumes: The H Flume features a V-shaped design that facilitates the measurement of a very broad range of flows, from extremely low to very high. Initially designed by the U.S. Forestry Service as a portable flume, the H flume is used broadly to measure runoff from farms. Some of the typical measurement applications for H flumes include:
    •     Agricultural water runoff
    •     Holding pond overflow
    •     Industrial process discharge
    •     Irrigation water
    •     Storm/sanitary sewer discharge
    •     Snowmelt
    •     Watershed runoff

Flume Instrumentation Accessories

With the help of various flume instrumentation accessories, you can monitor and measure flow rate, water pressure and depth, and more.

Staff Gauge

These gauges, or rulers, come in a wide array of sizes, based on the scale of their installation location on a wall. There are also several types of staff gauges available on the market to fit your application.

Ultrasonic Transducer

Ultrasonic transducers are sensors that produce a pulse of sound to gauge the water level of a flow. Once the pulse reaches the water’s surface, it will rebound back to the transducer, which is installed above a flume’s inlet. The sensor then measures the amount of time between the pulse generation and its return to make its calculations.

Pressure Transducer

These transducers monitor water pressure to determine flow rate within a channel. Rather than installing them above the water’s surface, these transducers are submerged and mounted to the base of a channel. A probe on the pressure transducer compares the water pressure to the proportional flow depth to arrive at a rate-of-flow measurement.

Bubbler Sensor

Like a pressure transducer, a bubbler utilizes a sensor component. In this case, however, it is a tube rather than the sensor that is placed beneath the water in a channel. The tube is connected to the bubbler sensor, and the sensor determines water pressure by measuring the air pressure within the tube at the base of the channel. From this information, the sensor can generate water depth data.

Mag Meter

Mag meters, otherwise known as electromagnetic flow meters, consist of two vital components: a sensor and a transmitter. These parts coordinate to calculate water flow and pass that information on to a control system. The inline sensor monitors the amount of voltage that the water flow creates in piping, logs it, and the transmitter translates that voltage data into a water flow value for the system.


Contact Virtual Polymer Compounds, LLC for Premium Fiberglass Flumes

At VPC Fiberglass, we specialize in creating durable and cost-effective specialty fiberglass components and structures for commercial, industrial, and municipal water and wastewater applications. Our company designs and fabricates custom or standard Parshall flumes, H flumes, Palmer-Bowlus flumes, and trapezoidal flumes through state-of-the-art technology. We also have restoration and repair capabilities to provide our customers with comprehensive service. 

Our team will collaborate with you from conception through component installation to ensure satisfaction. Browse our catalog for more information on our product line, or you can contact us today to learn more about our capabilities. Once you are ready to begin your project, request a quote to hear from our team.