Boilers operate at low pressure to prevent pressure from building when the water is heated. The system must have a place for this water to go that is the job if the expansion tank. Heated water pushes against the diaphragm pushes the water back into the system.
Item Tag: 11.25 in
Constructed from lightweight, durable corrosion-resistant aluminum with stainless-steel lever and fitted with an easy-to-read pressure indicator, the heavy-duty valve assembly is made for years of service.