To control the liquid level in the draining tank three equipment changes are necessary.
First, we have to measure the level, and we have selected a pressure difference sensor for this purpose.
Second, a control valve is needed to provide a variable resistance in the outlet pipe from the tank. This is one possible configuration to control this self-regulatory system.
Third, a calculating device is needed to perform the controller calculation. This would normally be a digital processor with communication with the sensor and valve.
Note: A pump is not required unless the liquid head in the tank is not sufficient to provide the desired flow rate.