WHAT IS AN EXPANSION TANK?

[SHARON]

WHAT IS AN EXPANSION TANK AND WHAT DOES IT DO, IS IT REQUIRED BY CODE?

[MikeM]

From Wikipedia, the free encyclopedia
An expansion tank or expansion vessel is a small tank used in closed water heating systems and domestic hot water systems to absorb excess water pressure, which can be caused by thermal expansion as water is heated, or by water hammer. The vessel itself is a small container divided in two by a rubber diaphragm. One side is connected to the pipe work of the heating system and therefore contains water. The other, the dry side, contains air under pressure, and normally a car-tyre type valve for checking pressures and adding air. When the heating system is empty or at the low end of the normal range of working pressure the diaphragm will be pushed against the water inlet. As the water pressure increases, so the diaphragm moves compressing the air on its other side. The compressibility of the air cushions the pressure shock, and relieves pressure in the system that could otherwise damage the plumbing system.

When expansion tanks are used in domestic hot water systems, the tank and the diaphragm must conform to drinking water regulations and must be capable of accommodating the required volume of water.

In the past, domestic plumbing systems often contained more air than they do currently. Thus, expansion tanks are now used more frequently than in the past.

Expansion tanks are only required in new construction, remodels and commercial applications. Existing homes in Utah are not required to have on installed when replacing your water heater.