In a steam boiler system, blowdown involves removing a portion of the concentrated boiler water and replacing it with feedwater, which is a mixture of condensate and makeup water.
Good blowdown control is a critical component of the boiler water treatment program. Boiler blowdown is heated, treated feedwater that is sent to the drain instead of converted into steam. Blowdown is used to control the dissolved and suspended solids level in a boiler within the range necessary to minimize scale deposits and carryover. Too much blowdown increases fuel, water, and treatment requirements. Too little blowdown can cause scale deposits and wet steam (carryover)