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Fluctuating Water Tower Levels?

Good morning,

I am working on a water system project and one of the water tower's levels is fluctuating frequently. To provide some background - there are two towers in the system. I am trying to set up controls such that they both fill with the pump on, and then the pump turns off and both towers empty. One tower does this (see picture), but the other tower's levels keep fluctuating. It looks like the tower is rapidly filing and emptying (see picture). Why is one tower doing this and the other tower not? How can I set up the controls such that this doesn't happen? 

Thanks,

Allison

  • I assume that the graphs are of model results not field data and both tanks are in the same pressure zone.

    Is the red tank a lot smaller than the blue one? Check the diameter/cross section.

    Is there some type of control that is close to the red tank. For example a pump that pumps into a higher zone.

    Is there a major user near the red tank with a strange demand pattern? Do you have roughly the same demand pattern across this pressure zone?

  • Hi Tom, thanks for your response. Both tanks are in the same pressure zone and the graphs are of model data. There is only one pressure zone for the municipality. The red tank is about 1/5 the size of the blue tank. There are no pumps that pump into a higher zone near this tank. Demand patterns are consistent across the municipality; although, this tower is located about ~6-miles away from the rest of the town (see picture). It will service businesses at an interstate interchange (total demand ~30-gpm).

    Would the tower's placement so far away from the rest of the municipality cause the rapid fill/empty cycles? 

  • Which tank controls the pump cycling? I'm guessing it's what I called the red tank. Because it is small, it fills more quickly and because it is far away from the source (I'm assuming)  it drains more quickly.  

    I can't explain why the father tank water elevation can get higher than the nearer tank. Is it filled/drained by much larger pipes?

  • The controls are set up such that the larger/blue tank controls the pump cycling. If I switch the control so the smaller/red tank is controlling the pump cycling, the small/red tank is still cyclical, but the cycles are smaller (see picture). Both tanks are filled/drained by 10-inch pipes. 

  • Hello Allison,

    Could you provide a copy of the model files to us? That may help to identify what is happening here. The following link has the steps to securely send the model files: Sharing Hydraulic Model Files.

    Regards,

    Scott