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Thread: No Flow To/From Tanks

  1. #1

    Join Date
    Aug 2017
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    1

    No Flow To/From Tanks

    While running an extended water quality model on a large system, several of the water tanks in the system seem not to interact with the rest of the system correctly. For example, one tank shows no flow in or out of the tank for the entire duration of the model (15 days). Consequently, the volume of water in the tank never changes, and the water age increases with time at a 1:1 rate. Another tank shows flow in and out for portions of the simulation, but experiences regular periods with no flow whatsoever.

    Any ideas on what might be preventing the tanks from interacting with the system for extended periods?

    Thanks,

    Will

  2. #2
    Forum Moderator

    Innovyze Employee



    Join Date
    May 2015
    Posts
    287
    Will,

    Thank you for posting your question. Here are a few things you can investigate assuming you are using InfoWater. Please reply if you are using a different platform.

    1) Water flows from high head to low head. If the head in the tank is below the head outside and the tank is not 100% full water will generally fill the tank unless there is something outside the tank restricting flow in or flow out of the tank. Similarly if the tank head is higher than outside water will flow out of the tank (assuming nothing outside the tank is restricting outflow. Take a look at the head at the tank and at a junction outside it to see what the water should be doing. Without knowing this it is impossible to say what might occur
    2) Is the tank going 100% full or 0% full? When this occurs EPANET (InfoWater's hydraulic engine) will close all pipes connected to the tank and temporarily no flow will go in or out of the tank. Generally, if you set pump off controls to the max level of the tank the pump will not turn off as simple controls say turn of if "greater" than the max level, which cannot occur. If this happened your tanks would fill, but would get "shut off" by EPANET and could not drain unless the demand increased enough so that the pumps cannot meet 100% of the demand. Thus you could easily have periods that could respond exactly as described.
    3) Review your pump and or valve controls that are used to fill the tank. Check that "off" controls use a tank level below the maximum level of the tank. Make sure valves used to fill a tank use a "setting = X" control to turn on as a status = Open type control will simply make it act like an open pipe.
    4) Do you have a check valve or other feature restricting outflow from the tank. Verify check valve pipe direction as water can only flow in the direction the pipe is drawn. You may also want to check for closed pipes as this could also interfere with the tank filling/draining. There is a special query in the domain manager under pipes for check valves and pipes initially closed or with controls that will put them in the domain to help you find pipes closed or with check valves as well.

    Generally one of these 4 things is often the reason tank operation is not what is expected. Take a look at these and they should help you find out why this is occurring.

    Post back if you need help or reach out to us at Support@innovyze.com if you need further assistance.

    Patrick Moore

    PS: for Water age if your tank still shows the 1:1 45 degree angle that tank has not reached steady state yet and you may need to run the simulation longer. But resolve why the tanks do not drain first as water age will never stabilize if no new water ever enters the tank.


    Quote Originally Posted by wcmenk01 View Post
    While running an extended water quality model on a large system, several of the water tanks in the system seem not to interact with the rest of the system correctly. For example, one tank shows no flow in or out of the tank for the entire duration of the model (15 days). Consequently, the volume of water in the tank never changes, and the water age increases with time at a 1:1 rate. Another tank shows flow in and out for portions of the simulation, but experiences regular periods with no flow whatsoever.

    Any ideas on what might be preventing the tanks from interacting with the system for extended periods?

    Thanks,

    Will

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