An expansion tank has a chamber in which air is locked inside a bladder or diaphragm.
It screws into standard 1/2-inch or 3/4-inch threaded plumbing fittings. When
pipes are filled with heat transfer fluid (water and glycol), and the operating
pressure of the system is set, the fluid will occupy a given volume based on
the temperature. As the fluid is heated by the sun, it expands. The expansion tank
allows the fluid to safely expand by compressing the air in the chamber. The
size of the expansion tank needed depends on the total volume of fluid, which is
determined by the number and size of collectors, and the length and diameter of
the pipes in the solar loop.
Expansion Tank
