Issues with pump head

Question

Ref : https://communities.bentley.com/products/hydraulics___hydrology/f/haestad-hydraulics-and-hydrology-forum/155666/how-to-replace-hydrants-to-nodes-and-add-prv-to-fix-7-bar-pressure-head-at-fire-hydrant 
 Hi Tom/Bentley Team, 
 I have an issue with Head at pump, if I give 90m head then the model is working fine and not meeting 7.0 bar pressure head criteria at fire hydrants. if I give 118m head, most of the hydrants are disconnected from the system and not meeting 7 bar pressure head criteria at fire hydrants. 
 please see my model attached for your reference. 
 4857.Fire Hydraulic Model - REV-06-2.zip

Yashodhan Joshi · Answer

Hello Gangadhar, 
 I checked your model and could see the following user notifications; 
 " System disconnected because of PRV PRV-1 " : This is due to the fact that the PRV Status (Calculated) is "Closed" i.e. PRV-1 has to close in order to reduce the pressure at hydrant H-1, which is causing the system to be disconnected. This is also due to the fact that there is no demand assigned to the hydrant H-1. If you assign demand then the PRV wont close and your system would also remain connected.

" Hydrant FH-XX is disconnected from a reservoir or tank during the analysis " : This is also due to no demand assigned to majority of the hydrants. Once demands are assigned, this notification won't appear. 
 If you are performing fire flow analysis at selected nodes then it is suggested to use the fire flow alternative. 
 Hope this helps.