Skip to main content

How to Install a Weir

Weirs are sensitive to installation conditions.  Poor installation is many times not correctable, so it is important that the following be used when installing a weir plate.

Installing the Weir

  • The crest (flow edge) of the weir must be set 2-3 times Hmax above the floor of the channel.
  • The crest of the weir must be set at least 2-inches [5.08 cm] above the maximum downstream water level.
  • The widest portion of the weir crest at Hmax should be at least 2 times Hmax from the sidewall of the channel (on each side).
  • The weir must be centered in the channel.
  • The weir must be level from front-to-back and from side-to-side.
  • The crest must be horizontally level.
  • If present, the bevel of the weir crest must be set downstream.
  • In earthen channel applications, the channel downstream of the weir should be reinforced / armored so that scour does not occur.  Scouring can lead to the weir plate shifting out of position or flow bypassing the weir plate.