alternating pumps or pump cycles in watercad - Haestad | Hydraulics and Hydrology Forum - Haestad | Hydraulics and Hydrology - Bentley Communities

alternating pumps or pump cycles in watercad

Hi everyone.

    I have had addressed this issue before (almost an year ago) but due to some reasons we discontinued working on the project and we started working on it again recently.

I am running an EPS run on a system with three pumps controlled by a tank. Pumps 1 and 2 are smaller ones which pump 700 and 650 gpm and pump 3 is a larger one which can pump up to 1300 gpm. I have my initial tank level at 469. The way i want to run the model is that when the tank level drops to 465, pumps 1 and 2 turn on and fill the tank back up to 469, and when the next time the level drops to 465 pump 3 should turn on and fill the tank up. Is there a way I can make this thing run in this way, so that i can alternate the pumps, like pumps 1&2 for first cycle and pump 3 for next cycle and so on.




3 Replies (Most Recent Reply)

  • If you submit a service ticket to technical support at we will be more than happy to help you with the problem that you are having


  • In reply to MPachlhofer:

    I would say its not a problem, but iam just willing to know what type of controls i can use, if there is any to run this type of simulation. Like i never alternated pumps earlier. Just want to know if this type of run is possible with watercad.

  • In reply to vkeppakayala:

    I think there is a way you could do this, but it will be a little bit complicated and you'll have to live with some warning messages.

    First, create an extra pipe in your model and for convenience, attach it somewhere near your pump station.  The size of it doesn't really matter because it should never convey flow. It can run off to a dead end junction or it can be in parallel like in the picture I've attached.  Either way, something is going to be hydraulically disconnected, which will generate yellow warning messages during your runs, but shouldn't affect anything in your model.  For good measure, give it 0 slope and set it at the same elevation as the pipe it connects to.   To help the logic statements look more sensible, you might name it something like "Large Pump Switch".  You're going to use actions to toggle that pipe/switch open and closed so that you can write conditions to see whether you should turn on the little pumps or the big one.

    Then you'll need some complex conditions and actions.  They should look basically like this:


    C1: Tank Level <= 465 AND Large Pump Switch = Closed

    C2: Tank Level <= 465 AND Large Pump Switch = Open

    C3: Tank Level >=469 AND Large Pump Switch = Closed

    C4: Tank Level >=469 AND Large Pump Switch = Open


    A1: Pump 1 = On and Pump 2 = On

    A2: Pump 3 = On

    A3: Pump 1 = Off and Pump 2 = Off And Large Pump Switch = Open

    A4: Pump 3 = Off and Large Pump Switch = Closed

    Then, write your logic set like this:

    IF C1 Then A1

    IF C2 Then A2

    IF C3 Then A3

    IF C4 Then A4

    You could probably write just two control statements if you added ELSE clauses, but I found it easier to draw the logic flow up without use of the ELSE clauses.

    As I have it set up, the model run starts with the switch closed and Pumps 1 and 2 on and the tank near full.  The pumps run until they fill the tank, then turn off and open the switch.  When the water level gets to 465, because the switch is open, Pump 3 will turn on. When it has filled the tank, it will turn off and close the switch, so that when the water level gets low again, the two smaller pumps will be turned on and the cycle will begin again.  I got warning messages whenever the switch was closed, regardless of whether it was in parallel or a dead end.  I think you're going to have to live with that, but maybe someone will have a clever workaround for it.

^ Go to first post