The shut off valve stays at 4mm. In your case I'm saying you should leave it as is after the pump, so it should go: Pump ---> 4mm ball valve ---> filter ---> Turbine... The 6mm ball valve woudl be used on the feed line to the UAT.

My contact info is [link=http://www.pstna.com/service.htm]here[/link]. I don't currently have stock of the 4mm valves, but I'm placing the order later today. I have stock of everything else...

Kelly