OK... so I am still working on installing my toilet. I work at a snail pace.

I have an elongated commercial toilet being used in residential setting. It does not have a tank, but instead a column with a handle flush like you see at the mall washroom.

At the top of this valve column there are two functional items. The handle for toilet flushing, and a screw to stop the water (does it have an alternate function?). Unfortunately, when I open this screw the water fills in the bowl which is good.. but when the bowl is full and the valve assembly is then fully pressurized there is a water leak around this screw! How do I fix this? The water turn off screw is leaking.. that comes pre-assembled by the manufacturer. Its not like I can tighten it up or something. Well, I guess technically I COULD tighten it up, but then the water would be shut off to the toilet (it does not leak when fully closed).

Its brand new too...

Would a picture help?

Thanks for the advice :)