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Age analysis - Tank empty

Dear All,

I attached my water model for reference. the issue is, i am not getting correct result for age analysis "Age (maximum) (hours)"

In the model you can see "ADD + 10% for Age with reservoir" and "ADD + 10% for Age with tank and reservoir" as two scenarios for age analysis. Basically, the difference between scenario is water source as one scenario analysis with directly from reservoir and other with tanks.

I showed the results to client with "ADD + 10% for Age with reservoir". Since, there is no notifications in it. Further, u can see other scenarios apart from these scenarios. All those are worked with tank as water source. You can see the change in the active topology. these scenarios are working well.

Now, the problem is client needs the age analysis with tanks as water source as actual existing. So i tried, but notification shows all tanks are empty. (Note: all the tank details are actual as built). hence i inserted a reservoir for permanent source of water. After, introducing the tank, the notification says some times, tanks full or empty. since, i was not able to fix the elevation of reservoir.

Hence, how to fix this age issue with tanks. Further, I attached 2 squilte files one "Islandwide prposed 150mm and Without FF at existing SB area.wtg" is the one all iterations i done. other one "Original shown to client" is the one i shown to the client. the main difference we can see is the pumping station header main. I faced problem with the original for age in commmon discharge pipes with out flow. so i connected all the discharge pipes at one point.

expecting the Solution.


  • Hello RSP,

    I took a look at the model and I need a little more clarification about what is wrong with the Tanks. From looking at the scenario "ADD + 10% for Age with tank and reservoir" it is clear why the Tanks are filling. If you take a look at the Graph of any tank you will see that the Reservoir is filling the tanks almost immediately based on the higher HGL. Could you clarify how the real system should look? Is there a reservoir in the real system? You should be modeling the situation for the real system. This cannot be done by tricking the model with a reservoir simply because there are no User Notifications.

    Also, where are you seeing the Tanks as empty. Which scenario?

    This information will be very helpful.

    Thank you,


  • Hello Dan,

    These three tanks are fed by a 1200mm dia tranmission water line from a desalination plant 24X7.   So for this continuous source of supply, i considered a reservoir in the Model.

    The tank empty scenario comes in "ADD+10% for Age with tank and reservoir" if you slightly reduce the elevation of the reservoir. I was not to able to fix the elevation of the reservoir. Unless, the tank full warning is acceptable for the age calculation, in case of keeping the reservoir base level more than tank top level.

    Further there a age difference between scenarios, pumps directly connected from the reservoir  and pumps connected with tanks those fed by reservoir. though tank are full condition.

    Thanks for the effort,


  • Hello RSP,

    Let me clarify. You have three Tanks that are fed by a transmission line from a plant that you are modeling as a Reservoir. However, the Tanks are filling because the HGL of the Reservoir is causing the tanks to always be Full or Empty. How do the real tanks in the field look? Are they constantly full or empty?

    You may want to evaluate that Reservoir as your continuous source of supply.


  • Hello Dan,

    Three tanks are filled continuously. No intermittent supply.

    Main issue is based upon the elevation of reservoir, age in the distribution network is also differ. Just try by changing the elevation of tank with 3m, 2.5, 2 etc.  how to find the correct age in the pipes?

    If you see the other scenario, directly from the reservoir works perfect.



  • Hey RSP,

    Age Analysis works best when there is a fluctuation of Tank level. Since the Tank levels are always full it may be easier to get rid of the Tanks entirely and use the Reservoir as the sole source. Without intermittent supply, what is the point of these Tanks in the model?


    Dan Iannicelli