Open type expansion
tanks shall be located not less than 3 feet (914 mm) above the
highest point of the system. Such tanks shall be sized based
on the capacity of the system. An overflow with a diameter of
not less than one-half the size of the supply or not less than 1
inch (25 mm) in diameter shall be installed at the top of the
tank. The overflow shall discharge through an air gap into the
drainage system.