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» About flow regulation

» About flow regulators

About flow regulation

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When it rains....

A large number of sewage systems have inadequate capacity to transport those amounts of water which prolonged rain produces. When the water level in the pipes rises above a certain level, basements and other low placed localities are flooded. The result is - as most will know about – damages and pollution. Please see fig. 1 and 2.

Many waste water treatment plants are overloaded; the clarifiers do not have sufficient capacity to process, and additional amounts of pollution overflows into streams and lakes. During and after rain many overflow structures also dump large amounts of diluted waste water into streams and lakes.

If an oil trap is overloaded, the contents are whirled around and flow directly out into streams and lakes where they cause pollution.


Fig. 1: Flooding

Control the problem

Intense showers are often short and local, and they only cause full-flowing pipes in some places, and for a short time. The solution is therefore retaining the excess water in other places of the system during the relevant time interval. That is - where there is room for it - utilizing those places for storage.

The solution functions in far most precipitation situations and it does not require any investments in larger pipes or in basins, it only requires flow control with suitable flow regulators.

By effective flow control we mean a discharge which quickly reaches the maximum flow and stays at or below this value. This is the flow which there is room for without any problems after the flow regulator, further down in the system.

Generally speaking, the purpose of a flow regulator is protecting the low-lying parts of the sewage system (downstream) against overloading and flooding. A specific quality of the flow regulator is that it allows liquid to pass further down in the sewage system at a predetermined maximum amount per time unit, regardless the variation in feed flow and regardless the water level immediately before the regulator. See figure 3.

To avoid the risk of blockage and to minimize the need for service and maintenance, the regulator should be without moving parts. Furthermore, its passageway should be large to minimize its resistance in normal, daily runoff situations, and to avoid blockages.

Many options

It may prove necessary to build a storage facility if there is insufficient storage before the regulator.  This can be done by either expanding the pipe dimension over a short length or by building a basin.

The basin-solution ensures that damages will not happen after (downstream) the basin.  Please see figure 4.

When a regulator is mounted in a structure it is guaranteed that only that amount of water which the sewage system downstream of it is able to transport without flooding, will actually be transported further down.  The rest will be discharged into a lake or stream.

A regulator enables a property to respect the legislation on limited discharge during rain, i.e. from large parking lots or from large roof areas.

Similarly, a regulator can prevent overloading of a treatment plant, an oil/grease trap, a pumping station etc.

Mosbaek North America, Inc. • 3525 Piedmont Road • 7 Piedmont Center • Atlanta GA 30305 • E-mail info@mosbaek.com