Bilge tank compressed air question
 

So i am not sure if anyone can answer this but i have been wondering about how water is ejected from the bilge of a u-boat? Wolf pack seem to do it with compressed air but i have always had the impression it was done more commonly through the mechanical action of the electrically driven pumps?


What i have read seems to state that the main drain pump, auxiliary drain pumps as well as compressed air or portable hand drain pump could empty the bilge. While it seems compressed air is used in the operation of the main drain pump its not actually used to 'blow the tank'. unless the depth is excessive?


If anyone could shed some light that would be fantastic. tanks.


"the main bilge pump – two-stage rotodynamic self-suction pump: both stages could work in series connection (low efficiency when the pressure was high outside the hull at the depth of 105 m – 500 litres per minute at 2600 r.p.m.) or in parallel connection (high efficiency when the pressure was low outside the hull at the depth of 15 m – 1300 litres per minute). The pump was electric powered and was used to pump out a high volume of water out of the bilge, compensating tanks, torpedo compensating tanks or when there was a substantial hull leakage".

-http://www.kagero.pl/index.php?option=com_content&view=article&id=201:t he-viic-type-u-boot&catid=96&Itemid=686&limitstart=3

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