Terminology You will need to understand your: water system associated equipment, and be familiar with its constituent parts, such as: Dead/blind end – a redundant length of pipe, closed at one end, through which water cannot flow. Thermostatic Mixer Valves (TMVs) – these blend hot and cold water to reduce the temperature where a scald risk is present. Sentinel outlets – the nearest and furthest/last outlets from hot and cold water cylinders and tanks. Dead leg – a pipe leading to an outlet through which water flows but the outlet is unused/rarely used.