Hi there,

I am modeling a water treatment plant which has three wells pumping to a clearwell. In the model, I have set up three fixed reservoirs (the wells) which each individually go to a pump (well pump). The discharge from these three well pumps combine into one and then flow into a tank (clearwell).

In reality, the clearwell fluctuates between 51 ft and 54 ft. (I have set the size, level of the tank in the model to match the clearwell size in reality).

I want the well pumps to turn on/off given the clearwell level. i.e., the well pumps should TURN ON when the clearwell level falls BELOW 51 ft, and then should TURN OFF when the clearwell level goes ABOVE 54 ft.

I have set the following as my controls on these well pumps (T5000 is my clearwell):
Pump Controls.JPG

Each of the three well pumps has these same controls. The initial status for each of the well pumps is CLOSED and the initial level of my clearwell is 54 ft.

When I run the model, I am not seeing the results I expect to see for how these well pumps should be turning on/off.

Here is what my clearwell (T5000) is doing:
Clearwell Level.JPG
As you can see, the initial level is 54 ft. The lowest the clearwell gets is 51.21 ft. My impression of my controls is that this means none of the well pumps should turn on. They will only turn on if the level goes below 51 ft. Once it goes below 51 ft, the well pumps should stay on until the tank level goes above 54 feet again, at which point they would turn off. (Please correct my understanding if it is wrong).

However, the following is what one of my well pumps is doing (representative of all three well pumps):
Well Pump.JPG
The well pump is turning ON at Hour 1, and then it turns back off again. As the level in the tank never goes below 51 ft (as we saw above), I am mystified as to why the pump would turn on at all.

Any help/suggestions are much appreciated!