The quality of boiler feedwater is an important determinant of safe boiler operations and it should be monitored to maintain the quality within safe working limits.

Boiler feedwater is treated to protect the boiler from two basic problems: the buildup of solid deposits on the interior or water side of the tubes, and corrosion.

Scaling inside a boiler occurs as the salts in the boiler water get deposited when the water that contained these salts is evaporated to produce steam. Depending on the amount of solids in the water, or hardness, the rate of scaling varies. If left unchecked scaling can also destroy a boiler.

Boilers rely on the water to protect the steel boiler tubes from the temperatures in the furnace which greatly exceed the melting point of the tube material. A buildup of deposits inside the tubes produces an insulating layer which inhibits the water from removing the heat from the boiler tubes. If this continues long enough, the result is localized overheating of the tube and eventual tube failure.

In order to prevent the buildup of deposits on the tubes, the level of solids in the boiler feedwater must be reduced to acceptable limits. The higher the operating pressure and temperature of the boiler, the more stringent the requirement for proper feedwater treatment. Thus detailed and accurate logs of the feedwater and boiler water quality should be maintained and monitored regularly to ensure adherence to the safety norms.