Standard Orifice Static Tube, Model 9330

The USGS Standard Orifice Static Tube (SOST) is a modification of the standard orifice and is designed to reduce drawdown where water velocities reach 3 ft/s or greater.

The alignment of the SOST assembly is set at the time of fabrication and should not be altered. The SOST assembly vent hold must be positioned below the minimum water level. The assembly can be installed at any angle from vertical to less than horizontal. However, if the SOST assembly is not in the vertical position, it must be perpendicular to the flow streamline (that is, not pointing upstream or downstream).