HydroCAD Stormwater Modeling - Since 1986

HydroCAD Supports
Contech Filtration Products

StormFilter CartridgeHydroCAD provides full support for the Stormwater Management StormFilter offered by Contech Engineered Solutions LLC.

This partnership allows the flow effects of the StormFilter to be easily modeled within HydroCAD.

How the StormFilter is modeled

The StormFilter typically appears as an outlet device in HydroCAD, where it controls the discharge of water from an underground vault, which is modeled as a small pond.  The resulting analysis indicates the discharge throughout each rainfall event, as well as the water level inside the vault.  This information can be used to verify that the StormFilter will operate within its normal design range and provide the expected filtration performance.

Using HydroCAD-10

Because the StormFilter uses a unique float-activated mechanism, it cannot be modeled using a traditional stage-discharge curve.  The best approach for modeling the StormFilter is to use the new tube/siphon outlet in HydroCAD-10.  This option allows you to specify the start and break elevation for the particular cartridge, plus the effective diameters for the restrictor plate and trickle flow.  The Discharge Multiplier is set to the number of cartridges in the system.

Typical Vault InstallationAfter siphon flow is initiated, the flow rate is calculated by orifice flow, using the effective orifice diameter as listed below.  After the siphon breaks and the valve closes, the flow rate is determined by the effective "trickle diameter".  This behavior can be viewed on the pond's stage-discharge curve.

Cartridge Rating
(gpm @ head)
Effective Diameter Trickle Diameter
7.5 @ 120" 0.449" 0.263"
7.5 @ 18" 0.721" 0.263"
5.0 @ 12" 0.651" 0.263"
11.25 @ 27" 0.798" 0.263"
10.0 @ 12" 0.921 0.263"
15.0 @ 18" 1.020" 0.263"
22.5 @ 27" 1.128" 0.263"
All diameters are based on the default orifice coefficient of 0.60

Using HydroCAD-9.1

The original approach to modeling the StormFilter (in HydroCAD-9.1) was to use a pump outlet with a special predefined rating curve, plus a separate orifice outlet to model the trickle flow.  However, the tube/siphon option in HydroCAD-10 is much easier to setup and use, and is now the recommended solution.

If you must model the StormFilter using HydroCAD-9.1,you can use the pump outlet capability.  Although the StormFilter is a passive gravity-operated device, it exhibits a switching behavior that is quite similar to the on/off switching of a stormwater pump.

Note: Support for the StormFilter is included in HydroCAD 9.1 starting with build 20.  To check your version and build, see the Help|About screen in HydroCAD.  If you have an earlier build, please download the latest build using your existing HydroCAD 9.1 download instructions.

First, create a "pump" outlet and select the pre-defined rating curve for the desired cartridge configuration.  Next, set the number of cartridges and the operating elevations for the float valve.  Finally, define a separate orifice outlet to simulate the trickle-flow that occurs when the float valve is in the closed position.

Detailed product information

Click here to view pre-recorded webinarsFor detailed product specifications and design information, please visit the StormFilter product page.

For more information about HydroCAD

Please see the following pages for further HydroCAD information:

    HydroCAD home page
    Pond storage calculations
    Pump modeling
    General support page
    HydroCAD features and capabilities
    Free evaluation program
    Pricing and ordering

The Stormwater Management StormFilter is a registered trademark of Contech Engineered Solutions LLC
HydroCAD is a registered trademark of HydroCAD Software Solutions LLC
StormFilter illustrations Contech Engineered Solutions LLC


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