(1) Where air pipes to ballast and other tanks
extend above the freeboard or superstructure decks, the exposed parts
of the pipes shall be of substantial construction; the height from
the deck to the point where water may have access below shall be at
least 760 mm on the freeboard deck and 450 mm on the superstructure
(2) Where these heights may interfere with the
working of the ship, a lower height may be approved, provided that
the Administration is satisfied that the closing arrangements and
other circumstances justify a lower height.
(3) Air pipes shall be provided with automatic
(4) Pressure-vacuum valves (PV valves) may be
accepted on tankers.