Ball valves or seacocks are a must on all through hulls! A vented loop in your installation
would not help.... BUT a high water alarm
and good bilge pump
would until you could close the valve!
FWIW, When I rig a boat, I always try to cross connect my intakes (unless I can have a proper sea chest) with intervening valves, this way if one primary hose fails I don't lose water elsewhere when I close a seacock....Also, with such a set-up, if one TH clogs, I can source water from another and deal with the clog when convenient.