Measuring Wastewater Flows Underground

Water treatment system operators regularly need to measure the sewage flow in wastewater management and collection systems. Sewage flows are almost always under open channel flow conditions as opposed to through full pipes and are below grade. How this flow can be measured depends largely on whether an existing vault or fiberglass manhole is present. Learn about measuring wastewater flows underground and how to pick the right devices for your needs.

Measuring Wastewater When a Manhole Is Present

If a manhole or existing vault is present, you can often install a flow meter or flume into the structure. For the most part, the lines that run through these systems are only up to 12 inches, and the flows are small. The flume, in turn, must fit within the structure entirely.

You need to fit not just the flume but also its connections on each end entirely within the existing structure. Often, Palmer-Bowlus flumes are used for this purpose because they are specially designed for use with conduits and sewer pipes.

When You Don’t Have a Vault or Manhole

If you don’t have a manhole or vault and the flow is higher or the pipe size larger, it’s often necessary to build an entirely new structure to tap into the flow. For these purposes, a metering manhole is often used. A metering manhole with an integrated flume can extend from the manhole barrel either upstream or downstream of the manhole itself. You don’t need to install a large vault or try to force a flume to fit into the existing space.

When Does a Flume Need Help?

There are situations where you don’t want to use a flume alone. In wastewater applications, the use of a flume requires subcritical flow that is always under open channel, non-full-pipe conditions. These conditions are typical and almost always easy to meet in sewage systems, so it’s rare that you’ll need to use any other type of measuring system.

If the flow does need to be conditioned, however, you can place an energy-absorbing manhole upstream of your monitoring site. This structure can help to reduce the flow to measurable noncritical levels. It involves an energy-absorber plate placed perpendicular to the flow. This plate helps to break up the velocity and slow down the stream before it enters the flume.

The energy-absorbing manhole can be placed just upstream of the monitoring vault or metering manhole. If you have critical flow in your system, it can be an essential element in protecting against runoff and getting proper flow measurement and management.

Find Manholes and Flumes at Tracom

Choosing the right flume or manhole for your system is vital to the function of your wastewater and sewage monitoring and management. Fiberglass is a material that has a wide array of uses. It’s sturdy, can withstand many weather conditions, is relatively low maintenance, and can last for years. Tracom is your expert source for fiberglass manholes, packaged metering manholes, and fiberglass flumes to create the perfect system for your needs.

Check out our complete selection, and get in touch with us for more information, answers to all your questions, and to place your order today.

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Andrew Helbling

Andrew Helbling is the Product Specialist at Tracom, where he works with engineers, contractors, and product owners alike to assess and select the best open channel flow and general-purpose fiberglass products for their application. Andrew is passionate about clean water and helping operators and engineers provide the cleanest water possible.