The vent system has more than one channel on large transport aircraft and it is standard for the Boeing aircraft to have a pressure relief valve in the surge tank that works to relieve positive or negative pressure in the wing.
Can't find any reference to vent negative pressure relief regarding the surge tank vent valve in the Boeing 777 Maintenance Manual D&O. Is it mentioned in the (proper) AMM? Wouldn't the float valves
normally provide negative px relief?