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Pressure/PRV Issues

Hello,

I am trying to build a model for a development within another model that was made by someone else as part of much larger master plan.  My goal is to put in the pipes/valves/fhs/PRVs for our development into the existing model for the master plan area and achieve similar results in both models. I initially had trouble getting the PRVs to function similarly (I'm really only concerned with PRV-4,5,6 and EX1), but ultimately realized PRV-4 needed to be moved so that the flow wouldn't work to bypass the PRVs.  Now that that problem seems to have been cleared up, when I run the new model I get pressures in the ~2100psi range for the pipes that I've added (Y1-5, E1, E2, D1-3) and for the pipes from the Master Plan Model that connect those two areas (PS3-PS7) and I can't for the life of me figure out why I'm getting such unbelievably high pressures. 

I'm hoping that someone might be able to look at both of these models and explain to me why, through the addition of a handful of pipes, I end up getting such outrageous pressure readings in those pipes.  I don't know if it's due to the fact that I'm using the demand values and locations from the master plan model, maybe?

I would really like to use a stand alone model for our development, but the one I've created doesn't function properly in that the PRVs in the stand alone never have a flow or headloss, so I've resorted to trying to build my model within the master plan model. Any help would be greatly appreciated.

The Master Plan model is the 'Master WaterCAD Hydrant' and the new model is the '2019-08-12 Matrix_HKS_Proposed"Master WaterCAD Hydrant.wtg.zip2019-08-12 Matrix_HKS_Proposed.wtg.zip

  • Hello Justin, it looks like the elevation was not entered for some of the junctions. For example PS-J1, SE-FH2, SE-FH1, SY-FH3 and SY-FH2 all have elevations of zero. The pressure reported at those nodes is very high because it is calculated based on the difference between the hydraulic grade (which looks OK) and the elevation. In other words, the pressure is reported at the given elevation, and because it is over 5000 feet lower than the surrounding nodes (and boundary conditions), it shows as a very large pressure.

    See more in this related article from our Wiki: What does node elevation represent in WaterCAD, WaterGEMS and HAMMER?

    Also on the subject of modeling a smaller network that connects to a larger network, typically this is done by setting up a skeletonized version of the piping all the way back to the actual water source, using hydrant flow tests to model a single common connection point as a pump + reservoir, or approximating the connection(s) by using a fixed HGL at a reservoir based on the HGL at that connection location. See more here: Modeling a Connection to an Existing System


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.