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Flow Metering Manholes can be grouped into two types: open pipe and closed pipe. Closed pipe flow metering manholes use mag meters, clamp on meters, and insertion meters. Open channel manholes incorporate flumes, weirs, or direct sensing (radar, laser, or area velocity) meters.

In an open channel, freeboard is the head measured from the maximum water level to the uppermost watertight portion of the surrounding channel. Freeboard is an important consideration when evaluating the impact of the installation of a flume or weir. Weirs in particular require…

H Flumes can be a good choice when monitoring stormwater flows, whether mounting in a channel or at the end of a discharge pipe. H Flumes provide the low flow sensitivity of a thin-plat weir with the self-cleaning features of a flume. More than any other style of flume, H Flumes…

A hot spring is a natural upwelling of geothermally head groundwater. They can vary widely in temperature from those suitable for bathing to others so hot that immersion results in death or severe injury. Hot springs may contain high level of dissolved minerals (ranging from…

This overview provides information on the advantages and disadvantages of flumes for measuring the flow of water in open channels. Additional information is also provided on unique features and application notes on various flume types. Source: Teledyne ISCO Open Channel Flow…

This overview provides information on the advantages and disadvantages of thin-plate, sharp-crested weirs for measuring the flow of water in open channels. Additional information is also provided on unique features and application notes on various weir types. Source: Teledyne…

Sewer Surcharging is overloading the carrying capacity of a sewer system due to inflow and/or infiltration. As part of any inspection of a flow manhole site, the operator should look for signs of surcharging in order to ensure that their collection system is operating correctly.

Monitoring the flow of sewage is dirty and smelly, but that doesn’t mean it has to be hard! Many of the problems encountered in measuring surface and / or irrigation waters – high solids content, debris, the need to minimize head loss – are also present in sanitary…

When using a weir to measure the flow of water in a natural channel or man-made structure, one of two flow regimes are present: free-flow or submerged flow. Free-flow, also called modular flow, is when the discharge of the weir is not restricted by downstream conditions – where…

One question that comes up again and again is: Can Parshall flumes have the flow spill off the end? The answer is yes! While initially designed for installation in irrigation channels and canals, the Parshall flume has been shown to be well suited for use on free-spilling…

At its most basic a weir is nothing more than a structure over which water flows. Their simple design and wide range of styles offer certain particular advantages.

When mounting an ultrasonic sensor over a flume or weir one thing that frequently gets overlooked is the blanking distance - aka deadband - of the sensor. The blanking distance is that distance from the face of the ultrasonic transducer in which the flow meter will blank out (or…

Weir boxes provide the utmost in versatility when it comes to how the flow enters and exist the box. Flow can be piped inline, offset, or even free-spilling into and out of the box. However, sometimes this flexibility can cause problems when it comes to accurate flow measurement.

Tracer dilution is a method of determining the flow rate in a ground or surface water environment where a hydraulic structure (flume / weir) cannot be installed either due to cost, monitoring duration, or ecological reasons. The technique has been in use for over a century is a…

Flumes and weirs have historically been the tools used to measure the flow of water in natural and manmade channels. Either can be used by itself (with the operator taking manual level readings) or in conjunction with a secondary flow meter for automated data collection.

From time to time every weir installation will need periodic maintenance; whether to inspect the weir crest or to clean debris out of the weir pool. A simple and handy accessory to help with this is a clean-out opening or coupling. In weir boxes and manufactured channels, a…

Parshall flumes should not be placed at an elevation lower than that of the channel being measured for fear of inadvertently inducing supercritical flow in the flume (and a hydraulic jump) in the flume. Field observations have shown that supercritical flows can result in the…

The section of the weir that the water overflows is termed the notch or overflow section. If the notch plate is thin enough that the water springs clear of the downstream face, the weir is terms a sharp-crested or thin-plate weir.

In applications where equipment is large or cumbersome, it can be easier to remove / service the equipment by lifting it straight up and out! For those applications, Openchannelflow offers a removable roof option for our larger fiberglass equipment shelters. Modular construction…

The primary purpose of a stilling well is to provide a area were level measurements can be taken free of wave action or water surges. The surges and wind waves present in the main body of flow can be dampened by restricting the opening area of the inlet port.