The water tank is a storage area aboard a Galactica type battlestar for water in fluid form, and is part of a greater water system that is capable of processing and reclaiming water for use with negligible loss. At maximum efficiency, the ship can go years without outside replenishment.
Water tanks aboard a Galactica type battlestar are located close to the hull, with at least six tanks on the port side at the head of the ship, just above and ahead of the forward port landing bay. At least two large flexible tubes booming from the underside connect to a system that allows underway replenishment of spacecraft from these tanks.
The internal structure of the water tank features a walkway for use during maintenance, after the tank is sufficiently emptied. Otherwise, the pressures inside the tank would kill a human, even if suited (TRS: "Water").
Aboard Galactica, Sharon "Boomer" Valerii plants five G-4 explosives within the tank, detonating them to rupture both the inner and outer hulls, evacuating Galactica's water into space. After an investigation uncovers residue upon a honeycomb piece from the tank, it is determined by the Fleet's uppermost leadership that a Humanoid Cylon would have been responsible and that one such Cylon is aboard Galactica (TRS: "Water").
Later, Chief Galen Tyrol and Valerii make the mostly empty and repaired water tanks a location for their illicit romantic rendezvous (TRS: "Litmus").
Felix Gaeta stands in front of a water tank allocation chart (TRS: "Water").According to Commander William Adama, Galactica type battlestars have near unlimited capacity for water reclamation. While some of its capacity may be purified drinking water, it may also have greywater facilities for cleaning and other usages not inclusive of human consumption.
A chart at Felix Gaeta's briefing shows tanks 3, 5, 7, 9, and 11 on the port side of the "alligator head," different than the digital readouts from earlier in the episode (TRS: "Water").A flow transfer indicator during underway replenishment of Virgon Express from Galactica water stores (TRS: "Water").
The water tank's location near the hull may also help with buffering against radiation, as water is used as effective radiation shielding due to both its density and inexpensive nature.
Re-imagined Series definition: refueling and replenishment between ships away from dock, usually during flight. Taken from the contemporary term for the resupply of military vessels at sea while en route (TRS: "Water", "Maelstrom")
