Inroads S&S Pit capacity on combination pits

Question

I have created a combination pit with grate and lintel but when the network is run the capacity of the combination pits seems too low. Reading the text it states that the capacity is roughly the same as the grated pit alown but my results are much less than the grated pit. I think I must have missed something.

Kevin McDonald · Answer

The capicity of a combination inlet will be the same as a grate inlet if the Curb Length value is less than or equal to the length of the grate. From the help... the Curb Length "specifies the length of the curb opening. If this length is longer than the length of the inlet, then it is assumed that the extra length of the curb opening is upstream of the grate. The capacity of the upstream curb opening is calculated. This capacity is removed from the total gutter flow and then the capacity of the grate is calculated."