two tanks control problem
So, in order to provide additional control for the second tank to the existing control for the first tank, I am planning to modify a little bit of the control circuit where, from the level sensor in the tank, it will send signal to the PLC in the panel. This PLC will send command for the valve to open, and hence will make the pump runs.


The panel and PLC won't have any of the controls or switchgear to read or operate sensors, valves and pumps on the second tank.
One thing you can do is add a manual multipole selection switch to choose the active tank.

The best thing is to hire the subcontractor to add features to the PLC for the second tank.

You can obviously hack a small control system that merges the two tanks into one tank. But you'll only be punishing the next engineers with unnecesary complexity.