High age in pump common header because of low flow

Question

Dear All, 
 
 I performed age analysis calculation for my water distribution model. I attached the screen shot of the model for reference. Here P-596, P-597, P-598 are the pipelines showing very high age because of very low flow in the pipe. I was not able to understand, that even pump delivers the flow of 26528.21 m3/d in the discharge side, why the flow in common header is negative?. From the attachment we can see that after the final node again the full flow is there. 
 i need suggestions to rectify the model. 
 Thanks, 
 RSP

Dan Iannicelli · Accepted Answer

First off, I assume that PMP-1, PMP-2, PMP-3 are currently off. 
 One idea is to attach all of the downstream pipes from the Pumps directly to the furthest discharge junction downstream of P-596. You will notice that the flows are correct if you add up, (P-127,P-617,P-619,P-627) compared with the discharge P-124. The issue is with the small connecting pipes. Try connecting the downstream Pipes directly to the common discharge junction. 
 Dan

Tom Walski · Answer

Assuming that you are running an EPS model and the flows displayed are the flow for a given time step, then it looks as if the model did not converge at the time step. Look at the Analysis > Calculation Summary. That should show you where the problem is. You may also want to run Analysis > Validate. 
 If that doesn't show you the problem, zip up the .wtg file and either the .mdb or .sqlite file (depending on the version) and send it to Tech Support. Tell them what version you are using. They are very good at solving these problem. 
 A value of -0.01 when dealing with flows this large is really just a zero with some round off. When you are dealing with flows on the order of 100,000, it is best to use Units and Formating (right click on flow) and set the number of decimal places to zero because values after the decimal point are misleading and clutter up your results. There is no way that you know the flow to 8 significant figures.