The quality of the water used to produce the steam in the boiler will have a profound effect on meeting the objectives such as safe operation, maximum combustion and heat transfer efficiency, minimum maintenance and long working life.

As a result, there is a need for the boiler to operate under the following criteria:

1. Freedom from scale - If hardness is present in the feedwater and not controlled chemically, then scaling of the heat transfer surfaces will occur, reducing heat transfer and efficiency - making frequent cleaning of the boiler necessary. In extreme cases, local hot spots can occur, leading to mechanical damage or even tube failure.

2. Freedom from corrosion and chemical attack - If the water contains dissolved gases, particularly oxygen, corrosion of the boiler surfaces, piping and other equipment is likely to occur.

If the pH value of the water is too low, the acidic solution will attack metal surfaces. If the pH value is too high, and the water is alkaline, other problems such as foaming may occur.