Loss Library Manager

The Loss Library Manager lets you browse built-in libraries, create custom libraries, and configure junction loss equations for your projects. Each library contains a collection of loss types that define how energy losses are computed at different structure types.

Opening the Manager

Open the Loss Library Manager by clicking Manage next to the Design standard selector in the Structures Table.

Library List (Left Pane)

The left pane displays all available libraries, organized by category:

• Standards — Built-in libraries based on published engineering standards (HEC-22, iSWM/NCTCOG)
• State — Libraries tailored to specific state or regional standards
• User Libraries — Custom libraries you have created or copied from built-in templates

The active library (the one used by the current project) is indicated by a filled circle icon. Built-in libraries are read-only — to customize one, you must copy it first. You can use the Hide/Show toggle to hide built-in libraries you don't use, keeping the list focused on your active libraries.

Built-in Libraries

HydraStorm ships with three built-in libraries:

Library	Description
User Starter	Default for new projects. Contains generic loss types with simple K × V² / (2g) expressions. Designed as a template — copy it to create municipality-specific libraries.
HEC-22 Standard	FHWA HEC-22 4th Edition (2024, HIF-24-006) §9.1.6.7. Manhole entry uses the 3-step access-hole energy method Eai = max(Eaio, Eais, Eaiu) with corrections per Eq 9.27 and exit loss per Eq 9.31. Bend, wye, transition, and exit entries use expression-based forms of Eq 9.6, 9.9, 9.7–9.8, and 9.5.
iSWM / NCTCOG	NCTCOG iSWM 2014. The manhole entry uses the HEC-22 2nd Edition compound K method (K = Ko × CD × Cd × CQ × Cp × CB) — iSWM 2014 §1.2.10 reproduces those equations verbatim as Eq 1.36–1.42. Bend/wye/transition/exit entries use expression-based forms of iSWM Eq 1.29, 1.34, 1.30/1.31, and 1.28.

Library Properties (Right Pane)

When you select a library, the right pane shows its properties and loss types. The properties section includes:

• Display Name — The name shown in dropdowns and the library list
• Source Citation — Reference to the engineering standard or manual the library is based on
• Version — Version number for tracking updates to the library
• State — The state or region the library applies to (optional)
• City — The municipality the library applies to (optional)
• Use in Project button — Activates this library for the current project

Loss Types Grid

Below the library properties, the loss types grid lists every loss type defined in the library. Each type defines:

Field	Description
Name	Descriptive name for the loss type (e.g., "Straight Run Manhole", "90-Degree Bend", "Wye Junction")
Group	Category for organization (e.g., "Manhole", "Bend", "Wye", "Inlet")
K Value	Base loss coefficient used in the expression via the K variable
Equation Kind	One of three computation methods: ExpressionString (user-authored formula), Hec22EnergyLoss2ndEd (compound K method, also used by iSWM/NCTCOG), or Hec22EnergyLoss4thEd (3-step access-hole energy method). See Junction Losses for details.
Expression	The mathematical expression used when Equation Kind is "Expression"
Inflow Expression	Optional override expression used when the structure has captured surface runoff

Creating a Custom Library

There are two ways to create a custom library:

Option A: Copy from a Built-in Library

1. Select the built-in library you want to start from in the library list.
2. Click Copy. A new editable library is created with all the loss types from the original.
3. Edit the library properties — update the name, citation, state, and city to match your jurisdiction.
4. Modify the loss types as needed: adjust K values, edit expressions, add new types, or remove types that don't apply.
5. Click Save.

Option B: Create a Blank Library

1. Click New to create an empty library.
2. Fill in the library properties (name, citation, etc.).
3. Add loss types by clicking the add button in the loss types grid.
4. Configure each loss type's name, group, K value, equation kind, and expression.
5. Click Save.

Equation Editor

Double-click a loss type (or select it and click Edit) to open the Equation Editor. This provides a dedicated interface for authoring and testing loss expressions.

The editor includes:

• Expression field — Enter the K_j formula using the available variables and functions
• Variable palette — Reference panel showing all available variables with descriptions, so you don't have to memorize variable names
• Functions reference — List of available functions (sin, cos, sqrt, pow, min, max, deg2rad, vh, etc.)
• Test with sample values — Enter sample variable values and evaluate the expression to verify it produces the expected result before saving