water network model

[WaterGIS]

hi all,
i have recived a water network model, this model consists of UPVC pipes 200 mm, when i run the model through watercad i faced some problems mainly that velocity is going higher than 1.5 m/s and lower than .3 m/s and start increasing the pipes diameter but this did notwork to decrease the velocity
then i used darwin analysis, and the resulted pipes where much smaller than the 200mm , and when i run the model again it did not satisfy the min and max velocities
im really confused!!!
any suggestion
many thanks

 

[BigInch]

Put some maximum pressure, or flow limits in there. If you just increase diameters, you will higher flows, which is keeping velocities relatively equal.