Unexpected High Flow - WaterGEM

Question

When I was working on Steady State analysis of a system with 8,310 gallon per day demand, I realized that one node with 2.36 gpm demand had 23.6 gpm demand instead. At that time, steady State was working. I corrected the demand at that node, which should decrease the total demand by 30,585.6 gallon. But, when I re-run the steady state, 3,600 gpm flow is trying to go to the node. We could not figure out why. There is no such demand assigned. 
 We need to make this model work as soon as possible. I wonder if someone could give us an advice on what to look for. 
 Yoko

Scott Kampa · Accepted Answer

Hello Yoko, 
 
I assume the scenario that you are running is "1-Stead State Analysis". This appears to have a demand of 2.36 gpm and a tank level of 1397 ft. If you are looking at a different scenario, please let me know. 
 
When I compute the model as is, I get a "Network Unbalanced" message, meaning the results cannot be trusted. I made a few changes to the calculation options to fix this. First, I increased the number of trials to 100. Second, I set the Damping Limit to 0.01. With this changes, the model was able to compute without an error message. 
 
After the changes, the pump flow results for pump "PMP-Distribution" was about 47 gpm. Flows in WaterGEMS will always satisfy the demands, but it will also balance the hydraulic grade across the system. The additional flow not going to demand is filling the three tanks downstream of the pump. The general results appear to be reasonable based on what I am seeing. 
 
Regards, 
Scott