TRU-BEND (Overflow Bending Weir)

The TRU-BEND Overflow Bending Weir System is designed to maintain maximum water levels upstream of the weir thus allowing full usage of all the available upstream storage volume while not adversely affecting the overflow weir capacity in Combined Sewer Overflow (CSO) applications. The TRU-BEND’s unique and extensively tested design operates by only allowing any excess water in the system to reach the receiving stream but only after the design upstream water level is reached. This increases the tank and sewer storage volume and reduces the frequency and volume of overflow events, resulting in a decrease in water pollution. This allows the TRU-BEND to overcome the fixed weir’s inherent disadvantages. The TRU-BEND protects against backflow as it is normally in the closed position.


The TRU-BEND allows for installation in new overflow structures or can be retrofitted directly over existing fixed weirs. The following components are included in the TRU-BEND Overflow Bending Weir System: the bending weir flap, the sleeve bearings, the supports, the guide walls, the anchoring system, the counterweight system and the inclinometer.


  • Counterweights rarely come into contact with debris
  • No need for bottom clearance
  • Maximize in-situ storage
  • Constant & easily adjustable operating level
  • Reduce overflow frequency
  • Backflow prevention
  • Improved hydraulic grade line
  • Lower storage tank construction costs owing to smaller tank volumes
  • Easy to retrofit into existing installations
  • Stainless steel construction

Range of Application

The TRU-BEND Overflow Bending Weir System can vary from a model GTB-30 to GTB-150. The GTB-30 is designed to hold back 12 inches (30 cm) of water over the weir crest and the GTB-150 holds 60 inches (150 cm) of water over the weir crest. The TRU-BEND’s model selection is based entirely on the height of the storage water required. The units are modular in design with a single unit being up to 30 feet (9 m) long. The hydraulic capacity of the TRU-BEND is at least equal to that of a standard overflow weir.

System Operation

The TRU-BEND overflow bending weir is installed on the downstream side and directly over the entire length of the overflow weir opening. The TRU-BEND accommodates the overflow by pivoting at the bottom and swinging open from the top.


The bending weir mechanism is entirely passive and does not require any external energy for operation. The fixed counterweights act against the bending weir flap to maintain a constant upstream water level for all overflows varying from 0 to the design flow. The TRU-BEND overflow bending weir will remain fully open and act as an emergency overflow to accommodate flows greater than the design flow with a resultant increase in the water level. The operating level can easily be adjusted on site by adding or removing counterweights.


The TRU-BEND overflow bending weir does not require any controls, however operation may be monitored by an inclinometer. The upstream and downstream water levels may also be monitored.