The deaerator is an open-faced water heater which removes non-condensable gases from the feedwater. In addition to the condenser hotwell, the deaerator's storage tank is the remaining reservoir in the turbine cycle. Positioned below the deaerator and before the boiler feed pumps, the deaerator storage tank serves as a surge tank for the boiler feedwater. Tank level is often controlled by a control valve on the condensate supply line to the deaerator.
Pressure fluctuations are extensive in the deaerator storage tank and result in flashing. Level controls must contend with the tank's fluctuating temperatures and pressures.