Catch-basins of various diameters

[bmcmillan]

Has anyone ever modeled catch basins of various diameters? I think the default inlet is set for a manhole with a 4' diameter. How could I model an 8" yard drain on an 8" PVC catch basin?

[Chris Maeder]

You need to choose a grate inlet and specify the equivalent area for it that matches your yard inlet by specifying the width and length dimensions. Alternatively, choose a Neenah Foundry inlet that most closely matches what your yard inlet is.

[jhmiller]

I believe that the user is interested in accounting for the smaller volume of a 8" diameter junction (rather than the standard 4' diameter junction)... is there a way to 'decrease' the size of a junction, the way one would use a detention element to account for say a 6' or 8' diameter manhole?

[Chris Maeder]

To model a junction with a different diameter than a 4 ft diameter manhole, you need to instead use a storage node (we call them Detention Ponds in StormNET to simplify it for new users) and then define the storage area for the node using "Functional" and the area representing the 8" diameter yard drain.

[bmcmillan]

Chris thank you for replying to my post. As you recommended I have selected a specific Neenah Foundry inlet from the catalog which matches the size of inlet that I am trying to model. As jhmiller noted I am also trying to model the diameter if the entire inlet structure in addition to the grate itself. Is there a way that I can do that too? I'm not so concerned about the way the water enters the structure because the flow is small enough that no ponding will occur. However I want to accurately model the pipe/structure system and not have StormNET assume that more water can be stored in the structure than is really allowed. Are you saying it would be better to model this entity as a detention pond than as an inlet?

[bmcmillan]

Thank you Chris for your reply to my question. As you suggested, I have selected the appropriate Neenah Foundry inlet from the catalog. But as jhmiller noted, I would also like to model the entire inlet structure (not just the grate) with an 8" inside diameter. The area draining to this inlet is small so I'm not worried about the inflow and surface ponding related to the grate being so small. But since there are several inlets such as this in my network and the pipes fill up quickly I am concerned that StormNET may be modeling my system assuming that the inlet structures are a default 4' diameter and can store some water. I just wanted to make sure you understand what I'm trying to do with my model. With this explanation, should I still model these nodes as storage nodes instead of inlets as you mentioned earlier?

[Chris Maeder]

Note that there is no direct way define the catch basin storage volume other than modeling it directly as a storage node, as I detailed earlier. The catch basin volume is assumed to match that of a 4 ft diameter manhole.

Generally, the main storage volume to be concerned with is in the pipes and not the manholes. The pipe storage volume generally is a much larger percentage when compared to the junction node storage volume (i.e., whether you have a 4 ft versus a 5 ft diameter manhole, etc.).