Flow Measuring Manholes

fiberglass domed top flow measurement manhole with 2-inch parshall flume Packaged flow measuring manholes are a drop-in place solution to the need to measure, sample, and characterize the flow of water through a collection system. Flow measurement is commonly done where industries discharge to a POTW's collection system or at critical sections in a collection system. Flow measuring manholes are available with a range of top styles to allow the operator to specify a unit that installs where it is most convenient - from an access point of view - or which maximizes flow measurement accuracy.

Integrated Flumes

Industrial discharge is usually measured by small Palmer Bowlus, Parshall, Trapezoidal, and, occasionally, HS / H flumes. However, as the flow rates and line sizes are much larger in collection systems, Parshall and Palmer Bowlus flumes are almost exclusively used. Trapezoidal and HS / H flumes either do not have enough flow capacity (in the sizes that are easily integrated into a metering manhole) or are not deep enough to connect to the collection system's piping. Although they are avaialble in a wide range of lengths and throat widths, Cutthroat flumes work well in both industrial and collection systems applicatons, but are not commonly used due to their relative newness and customer's unfamiliarity.

While some agencies such as Trinity River Authority (Dallas, TX) and Metropolitan Council Environmental Services (MCES - St. Paul, MN) use large fiberglass vaults to encompass the entire flume with its end adapters, this approach adds significant cost with little additional benefit. As a result, most flow measurement installations involve standard Packaged Metering Manholes - where a portion of the flume is integrated into the manhole barrel - with any sections too long to fit extending out of the manhole barrel, covered, and laminated to the barrel to form a single-piece, watertight structure.

Manhole Covers

Traffic reducer tops (available with openings from 22 1/2" to 38") utilizing standard grade rings / frames / covers are available for installations in streets, parking lots, or anywhere vehicular traffic may be present.
Domed fiberglass tops - suitable for installations in grassy areas where vehicular traffic will never be present - provide operators with an installation that is easy to enter / exit and which can allow equipment to be installed in / removed from the manhole - useful when measuring industrial sites on a spot or short term basis.
Less common, aluminum tops are available where a low profile installation is needed capable of withstanding pedestrian foot traffic (but which will not see any vehicular traffic).