Boiler blowdown
![Surface blowdown is removed from the steam drum at the top of the boiler and Bottom blowdown is removed from the mud drum at the bottom of the boiler.](/Images/godic/202501/01/Steam_Boiler_3_english0544.png")
Boiler blowdown is water intentionally wasted from a boiler to avoid concentration of impurities during continuing evaporation of steam. The water is blown out of the boiler with some force by steam pressure within the boiler. Bottom blowdown used with early boilers caused abrupt downward adjustment of boiler water level and was customarily expelled downward to avoid the safety hazard of showering hot water on nearby individuals.