A closed expansion tank shall be sized based on the capacity of the system. The minimum size of the tank shall be determined in accordance with Section 1004.4 and shall be equipped with an airtight tank or other air cushion that is consistent with the volume and capacity of the system. Tanks shall be equipped with a drain valve and a manual air vent. Tanks shall be located in accordance with the manufacturer's instructions unless otherwise specified by the system design. Each tank shall be equipped with a shutoff device that will remain open during operation of the heating system. Valve handles shall be locked open or removed to prevent from being inadvertently shut off.