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Two Tanks, One High, One Low

Hello,

I have a situation with two tanks in my model (WaterCAD, standalone).

The current set up is thus:

The model - The larger of the two tanks is at a higher elevation, as are the piping and junctions for the larger tank. The smaller of the two tanks is at a lower elevation, as are the piping and junctions for the smaller tank.

Here are the current operating parameters of the two tanks:

T-1

Elevation (ft)                   553.46

Elevation (Base) (ft)        553.46

Level (Minimum) (ft)      17

Level (Initial) (ft)              18.5

Level (Maximum) (ft)     19.5

 

T-2

Elevation (ft)                   550.52

Elevation (Base) (ft)        550.52

Level (Minimum) (ft)      17

Level (Initial) (ft)              18.5

Level (Maximum) (ft)     19.5

The issue - The larger of the two tanks is flowing into the smaller tank according to the model (makes sense if the system is gravity fed). I need the two tanks to run in parallel because that is the current operation. 

The question - If the system is completely gravity fed, what valve or valves do I need to use to prevent the larger tank from flowing into the smaller tank, and have both run in parallel operation? I need both tanks to contribute to the system. I assumed a check valve would work to prevent the larger tank from flowing into the smaller tank, but I have no experience using them, so I am hesitant to.

Thank you for reading all of this,

Clint Taylor, EIT

Parents
  • Hello Clinton,

    In addition to Tom's response, can you tell us how both the tanks are filled? Are they filled through single source or separate pumps?

    Typically for a system with multiple tanks the higher tanks or tanks having higher HGL will fill the tanks with the lower HGL's first until an equilibrium is reached and then start supplying. In this case if the lower tank is continuously supplying the higher tank will continuously supply the lower tank to try to reach an equilibrium until its empty.

    In this case you can check your actual study and compare how both the tanks are emptying in the current operation. If there are any valves present on the pipeline or part of network connecting these tanks, you would need to study them too.

    For this case you can try something like a "back-flow preventer" type valve: How can I model a backflow preventer?

    However, it would be beneficial to use the same Elevation (Initial) for both the tanks to ensure they are operating simultaneously with the same HGL. 


    Regards,

    Yashodhan Joshi

    Bentley Technical Support

Reply
  • Hello Clinton,

    In addition to Tom's response, can you tell us how both the tanks are filled? Are they filled through single source or separate pumps?

    Typically for a system with multiple tanks the higher tanks or tanks having higher HGL will fill the tanks with the lower HGL's first until an equilibrium is reached and then start supplying. In this case if the lower tank is continuously supplying the higher tank will continuously supply the lower tank to try to reach an equilibrium until its empty.

    In this case you can check your actual study and compare how both the tanks are emptying in the current operation. If there are any valves present on the pipeline or part of network connecting these tanks, you would need to study them too.

    For this case you can try something like a "back-flow preventer" type valve: How can I model a backflow preventer?

    However, it would be beneficial to use the same Elevation (Initial) for both the tanks to ensure they are operating simultaneously with the same HGL. 


    Regards,

    Yashodhan Joshi

    Bentley Technical Support

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