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Fire Flow Analysis Downstream of a Pump

Hey Everyone,

I recently ran into the problem with WaterGEMS  that nodes on the downstream side of a pump do not have accurate "flows available" for the fire flow analysis results. The pumps in the model are still operating as if there isn't a fire flow and the "flow available" in the fire flow table is much lower than the maximum flow rate of the pumps. Is there an automated way to use the fire flow analysis for nodes down stream of a pump? or do you have to manually add a fire flow demand to each of these nodes so that the pump will operate at the higher flow rate? 

Thanks!

  • Scott,

    Error on my part, I was neglecting the the residual pressure constraint. Thanks for your help!

  • Hello Colin,

    I see that you also created a service request for this. I will answer in the forum so other WaterGEMS and WaterCAD users could potentially benefit from the conversation.

    This is likely related to the pressures in your system compared to the pressure constraints you are using in your Fire Flow alternative. In the fire flow results flextable, look for the columns "Pressure (Calculated Residual)" and "Pressure (Calculated Zone Lower Limit)." If either of these are at or below the pressure constraint you added for the fire flow node and the zone pressure, you will see the fire flow available will be less than the needed fire flow for the node. 

    If this doesn't help, there are other considerations. The fire flow available can be limited by a velocity constraint, if you are using that. Another optional item in the Fire Flow alternative is to consider the system pressure. Even if you have zones set up, if any node in the system is below the constraint, this can limit the available fire flow. 

    The following link has more information on understanding and troubleshooting fire flow results: Understanding Automated Fire Flow Results

    If this doesn't help, it would be useful to see a copy of the model files. This link has information on sending the files.

    Regards,

    Scott