Hydraulics plays a significant role in defining the phenomena in premise plumbing, so it is critical to have a thorough understanding to predict the water quality phenomenon at the fixture level. This chapter discusses the various hydraulic phenomena within the premise plumbing system (PPS) and water distribution systems (WDS) that have a direct impact on the integrity of PPS. It explains fundamental hydraulics in the PPS; hydraulic transients within PPSs and WDS, limitations of current modeling approaches, practical observations, and research recommendations. To measure hydraulic transient pressure variations in PPSs as a function of input parameters such as boundary head, valve positions, and transient triggering mechanisms, an experimental setup was designed to mimic the range of street-level pressures encountered in the real system. Hydraulic transients and pressure surges in water pipelines are pressure fluctuations caused by a change in flow conditions.