Low Flow Pipe for Water Quality Treatment

[urbanresource]

Hi all. First time post. I am trying to work on a design for a storm drain system in which I would be diverting low flows with the use of a weir. All low flows would be routed to an infiltration trench or drywell to allow for percolation in the the natural soil.

My question is whether any here has ever seen a custom made 12" PVC with a weir wall inside, used to divert flow. The low flow pipe would likely be a 4" pvc pipe. The reason for such a design is due to the restriction in the amount of space and clearance available. Typically, a junction structure or similar would be used to divert flows, but we just don't have the room to use this. Any feedback would be much appreciated.

 

[civilperson]

Use a wye, 6" x 12", with the six inch stub down. No need for a weir, just reduce to a four inch diameter and run to the french drain. When the four inch pipe is at capacity, then the excess flow will bypass the wye and continue down the 12" diameter run.

 

[urbanresource]

Unfortunately, running the stub down would likely be a problem with clearance requirements. This system would run in the ceilings of the subterranean garage. Would it be a possibility to run the 6" stub out of the side, with a reducer? Also, if it is determined that a 4" pvc might be too large, how would I further restrict the flow, without having to go down to a smaller pipe?

 

[RWF7437]

How about a simple orifice inserted in to the low flow pipe ?

 

[urbanresource]

The orifice would work if sized correctly. Have you seen this application anywhere? Sounds like a custom 4" pvc pipe with this orifice. Thanks for the response!

 

[gbam]

Have you considered a PVC catch basin (typically 18" in Dia.) with two out flow pipes. 4" pipe at bottom and the 12" raised above to meet you flow diversion?

 

[urbanresource]

A PVC catch basin was considered, but it would be difficult to install this as part of a system, that is located in the garages. Please note that this system is hanging in the ceiling, as I'm sure many of you have seen in underground garages (aka subterranean garage). Having anything too large could be a conflict with clearance. They typically try to provide 7 to 8 of clearance in the garages for vehicles.

The orifice idea provided by RWF7437 is an option I may consider. Any other ideas out there? I greatly appreciate the feedback!!