Nodes & Pipes Reference

This section details the physical parameters available for standard manholes (Nodes) and conduits (Pipes) within the platform.

Nodes (Manholes & Chambers)

Nodes represent junctions, changes in pipe direction, changes in pipe diameter, or physical inspection chambers.

• Cover Level (m): The absolute elevation of the ground surface at the node location. If the hydraulic grade line exceeds this level, flooding occurs.
• Invert Level (m): The absolute elevation of the bottom of the chamber (acts on pipe invert level / chamber). This forms the base elevation for the outgoing pipe.
• Chamber Size (mm): The physical diameter of the manhole ring. While rarely critical for basic hydraulics, it is vital for accurate bill of quantities and ensuring sufficient physical space for multiple incoming pipes.
• Catchment Area (ha): The impermeable area draining directly into this node. Rainfall falling on this area will generate runoff according to the Volumetric Runoff Coefficient ($C_v$).
• Additional Catchment Area (ha): An optional field to manually input extra area, typically used to enforce "Urban Creep" allowances (e.g., adding 10% to account for future paving) without altering the base CAD-measured area.
• Sump Depth / Storage / Flow Control: Additional node options to configure sump capacity, localized attenuation storage, or custom flow control devices directly at the node.

Outfall Types

The final node in any network can be an Outfall, or an outfall will be added automatically.

• Free: Discharges unimpeded into an empty water body.
• Surcharged (Fixed Depth): Discharges into a water body with a constant water level (e.g., a static lake). The engine maintains a constant head boundary condition based on the specified Depth above Invert.
• Variable Stage / Tidal: Discharges into a water body with a fluctuating level. You can define a continuous sine-wave tide (by specifying minimum and maximum tidal levels) or upload a custom Time-Depth curve to simulate river flood hydrographs.

Pipes (Conduits)

Pipes represent the physical conduits transporting water between nodes. The platform assumes circular cross-sections for standard gravity pipes.

• Diameter (mm): The internal bore diameter of the pipe. Standard UK sizes (150, 225, 300, 450, etc.) are used.
• Length (m): Automatically calculated based on the physical distance between nodes on the canvas. You can override this if the schematic length differs from the true length.
• Roughness ($k_s$): The Colebrook-White friction factor. A value of $0.6 mm$ is standard for modern concrete pipes. Plastic pipes may use lower values (e.g., $0.3 mm$), while old brick sewers may require significantly higher values ($3.0 mm +$).
• Slopes (1:X): Calculated dynamically using the formula: $Slope = Length / Invert$. Ensure your slopes meet self-cleansing velocity criteria (typically 1:150 for 150mm pipes).
• Flap Valve: A checkbox to install a non-return valve on the pipe. This prevents flow reversal (backflow), which is essential when discharging into a tidal outfall.