Venturi design experts please.

[AcroSteve]

I am working on my recirc skimmer again and I have a question regarding the optimal operation of a venturi on the inlet to a needle wheel pump. The pump is an Ocean Runner 3700.

I am trying to keep this a compact as possible. This results in the venturi being very near the impeller. There is 1.75" from the outlet of the venturi nozzle to the actual needle wheel in the pump. The length of the nozzle in the venturi is 1-1/2"

This pic shows the venturi assembly which will screw directly onto my pump.

Is this too close to the impeller for optimal operation? If so, should I try to re-design my plumbing to increase this disatance, and how much?

Thanks.

 

[AcroSteve]

Oh, is the location of the air hole critical too? Should I get it as close to the outlet of the nozzle as I can? Or, does it not make that much difference if it nerer to the inlet end of it?

I just want to do this right the 1st time, this time.