In case of glass tube type water level indicator for a boiler

• A. One end of the tube is connected to water space and the other is connected to steam space in the drum
• B. Both ends of the tube are connected to water space
• C. One end of the tube is connected to water space and the other end connected to chimney
• D. One end of the tube is connected to water space and the other end is connected to superheated steam outlet from superheater
• E. One end of the tube is connected to water space and the other is open to atmosphere