This paper presents the state-space modeling and control of a coupled-tank liquid level system. Observed-state feedback controller via eigenvalue assignment and LQG control are designed in discrete-time and implemented by an industrial controller PLC. Both control design methods are augmented with integral action for a reference tracking without steady-state error for step inputs. The aim of the study is to examine the control performances of the methods subject to reference tracking, noise attenuation, disturbance rejection. The experimental results are presented and discussed for this purpose.