Flow Sampling Manholes

Flow Sampling Manholes are specialized manholes designed for:

Measuring of wastewater / pre-treatment flows
Water quality sampling
Parameter monitoring

Flow Sampling Manholes are most commonly used by industrial dischargers as part of a city's / county's permit process for the release of pre-treatment flows to the sewer system. They are also used by municipalities and counties to measure in-system flows and where flows are sent to another agency's system for treatment (think city-to-county or city-to-city flows).

While existing concrete manholes can sometimes be repurposed to serve as Flow Sampling Manholes, it is more common to install a new manholes. The new manhole can be precast concrete or fiberglass.

Precast manholes, while cheaper to purchase, require the proper integration of the flume or weir. Done well and the precast manhole will be perfectly suitable for accurate for flow measurement. Down poorly and the results can actually be worse than otherwise could be achieved by using Manning's Equation (which itself is usually only good to +/- 20%).

a fiberglass Parshall flume precast into a concrete flow sampling manhole

Fiberglass Packaged Metering Manholes are much more conducive to safe and accurate flow measurement. Factory integration allows for a much wider range of flumes and weirs to be installed. In addition, larger flumes are only practical in fiberglass Packaged Metering Manholes or very large concrete vaults.

two-piece fiberglass Packaged Metering Manhole used for a municipal Flow Sampling Station

Packaged Metering Manholes used for flow sampling can be tailored to a wide range of site needs. Multiple top styles are available, including:

Domed Top fiberglass for grassy areas
Aluminum Top for pedestrian areas
H-20 Traffic Reducers for traffic applications

In addition to these standard tops, Packaged Metering Manholes can be provided with custom, iron, or grating tops as necessary.

an open top fiberglass Packaged Metering Manholes used as an industrial Flow Sampling Station

At ~1/10th the weight of concrete, Packaged Metering Manholes require substantially less equipment, manpower, and line downtime - all important considerations when installing a Flow Sampling Station.

Packaged Metering Manholes are available in a range of diameters (4', 5', 6', 8') and in depths up to 35' deep.