Precast concrete U-Drains (divided into two main types, Dry Weather Flow and Wet Weather Flow) are the industry standard for stormwater and surface water management. Though they don’t have international or national standards, unlike circular pipes, manufacturers like G Cast, OKA, Hume Concrete, and UCI Resources do converge on certain standard sizes, through market force and the desire for inter-compatibility.

Here is a breakdown of the standard dimensions you’ll typically find, categorized by the industry’s own naming conventions.

How Sizes are Measured #

U-Drain dimensions are always referred to by their Nominal Size (also known as clear opening or internal dimensions). This is expressed as Inner Pipe Width (PIW) by Inner Pipe Height (PIH), in millimeters (mm).

1. Standard Size U-Drains (Common Range) #

This category covers the most frequently used sizes, generally suitable for small to medium-scale civil and housing projects. They typically go up to an internal width of 1800 mm.

Common Standard Widths and Corresponding Depths (Inner Dimensions in mm):

2. Super Size U-Drains (Large Infrastructure) #

When it comes to large-scale projects like major highways, flood mitigation, or deep commercial drainage, you need U-Drains that can handle immense volumes. This is where “Super Sizes” come in. These units are significantly wider and taller, requiring specialized manufacturing and handling.

Super Size Widths and Depths (Inner Dimensions in mm):

Custom Sizes #

Manufacturers do get to manufacture custom sizes depending on needs.