Transient pressure waves in real pipe systems are affected by several phenomena not accounted for in the classic waterhammer theory. Damping mechanisms are differently manifested according to the material, configuration and existing features of pipe systems. The identification of dominant cause-effect relationships are major challenges in today's research for better understanding the physics of the phenomena, being able to mathematically describing them, and carrying out a successful diagnosis of existing problems. This paper aims at reporting observed transient pressure waves in different pipe rigs and at discussing the respective principal damping mechanisms associated to fluid-structure interaction, friction, and material retarded response. Discussion highlights differences in the response of each system in terms of wave damping, shape and timing.