What Does An Expansion Tank Do? Why is it Important?

What Does an Expansion Tank Do?

What does an expansion tank do and how does it work? The expansion vessel or expansion tank is a little tank that is utilized for the protection of closed water heater systems and residential water heating systems from high amounts of pressure. The expansion tank is filled partially with air. The compressibility cushions shock caused by the water hammer will absorb water pressure that is caused by what we know as thermal expansion.

The expansion vessel is a fairly smaller scale tank thats divided in 2 by a rubber diaphragm. 1 side of the tank is connected to the pipe-work of the heater system and contains water (H2O). The dry side holds air under pressure & often times, a Schrader-valve used for adding air and checking pressures. Whenever the water heating system is at the lower end of the typical range of working pressure or unoccupied, the rubber diaphragm is then pushed against the water inlet. The water pressure will increase, and the diaphragm will move to compress the air on the other side.

Older expansion tank styles were bigger and they were oriented horizontally. These older expansion tanks also had no rubber diaphragm that separated the water from it’s air pocket. This style is currently obsolete and were known for gradually transferring air from the tank to the peak point in the water system, due to the air dissolving in water, then coming out of the solution somewhere else in the system. This, required periodical draining of the tank and bleeding of the system, in an effort to maintain the effectiveness.

A rubber diaphragm in updated expansion tanks will prevent the undesired transfer of O2 and help maintain lower levels of oxygen within the pipes and reduce corrosion in the system.

When expansion tanks are used in residential hot water systems, the tank & diaphragm would conform to drinking water regulations & be capable of accommodating the right amount of volume

In past times, residential plumbing systems contained larger amounts of air air than they do today and all of the trapped air would aft as a crude expansion like tank. In newer and updated systems, expansion tanks are used much more often than in the past.

For more information go to Wikipedia, the free encyclopedia.