Definitions for cable tank
The Standard Electrical Dictionary
A tank in which a submarine cable is coiled away on board a cable-laying ship, or in the factory on shore for the purpose of testing or watching its insulation. Sometimes, in order to test it under pressures approximating to those it will be subjected to in practice, the tank is closed and the portion of cable within it is subjected to hydraulic pressure. This represents the pressure it will be exposed to in deep water.