Soundings must be taken carefully; they may be deceptive because of foamy oil or the rolling of
the ship. Furthermore, caution must be exercised in removing the plug or cap from the upper
end of a sounding tube. If the damaged compartment is open to the sea and outside water level
is above the top of the sounding tube, the upward rush of water or oil could prevent recapping
and result in flooding the higher compartment.
In preparing for a sounding, slowly back off the plug or cap. If a rush of air escapes around the threads while the
cap is still under control, tighten the cap immediately. No soundings are required to further determine that the lower
compartment is being flooded; but permitting more air to escape would permit more water to enter the damaged space.
A trickle of water appearing around the threads of the sounding plug indicates that the compartment below is
completely flooded. If either air or water is evident, resecure the cap and report the situation to the Damage Control
Officer indicating that the compartment has free surface water or solid flooding.
8-7. INVESTIGATION OF WATERTIGHT FITTINGS.
Investigation of structural damage by visual examination
presents many difficulties and dangers.
No watertight door, hatch, air fitting, oil fitting, cap, plug, scuttle, or manhole is to be opened
until it is known definitely that the compartment on the other side is either completely dry, or so
little flooded that opening the closure will not permit flooding to spread. Failure to do so could
cause additional flooding. Injury to personnel may result.
To do a thorough damage control investigation, it might be necessary to open one or more watertight doors or
hatches. It is unwise to open any such closures below the waterline in the vicinity of damage unless this is preceded by a
thorough investigation by means of soundings, and only after permission is obtained from high authority whenever the
situation permits. One mistake and the ship may be lost.
Many compartments are not provided with sounding tubes. This is no bar to investigation, however. Tapping on
a bulkhead with a hammer will often disclose the presence of water on the other side; the exact height of the water may
be judged by variation in the tones produced when the bulkhead is struck at different levels. Repair party crew members
occasionally should tap various bulkheads for practice to train their ears to the sound of bulkheads around undamaged
areas. The tones will vary appreciably with the thickness of the plate.