duravit in wall tank flush problems

I have installed a Duravit in wall tank (cistern), wall mounted toilet bowl and cannot get a complete flush> Duravit has advised me that the bowl has a down wash flush and does not completely evacuate the bowl with a gurgle like a conventional toilet. I've increased the water level as high as possible and still cannot flush solid waste. Any clues?

Thanks

Scott Pfaffman

Is the toilet vented properly? That can radically affect the quality of the flush.

Duravit flush problem

Yes the toilet is vented and the rough-in was inspected and signed off.