Hi! Could somebody help explain to me - in a simple way if possible - how ballast tanks function. what are the purposes of ballast tanks? Is ballast tank the same as ballast pump? And what does it mean when they say “the vessel was running on ballast”? I understand that the ballast tank has something to do with maintaining the balance of the vessel, but the articles I’ve read about regarding this matter mostly seem very technical and being a law student, it’s hard to understand.
One last question, in the event of grounding which causes a vessel to list dangerously and take in water, would the use of ballast pumps be of any help to refloat the vessel?
Thanks! 
ballast is, in simple definition, non-cargo material carried as weight to affect the way the vessel rides in the water. Back in the day, stone was carried as ballast, this is where east coast cobblestone streets come from. Today water is the most common ballast material. In some cases there may be “fixed ballast” which usually cement. Ballast affects a vessel in 4 ways; trim (front to back angle), list (side to side angle), immersion (lowering the vessel bodily in the water), and finally, stablity (keeping the shiny side up).
The definition of “in ballast” is that the vessel has no cargo on board is carrying ballast water to keep the shiny side up, propeller underwater and the crew from being rolled out of their bunks (and life otherwise live-able).
Ballast tanks are water tanks around the vessel. They are connected via piping to the ballast pump and the outside of the vessel via a “sea chest” which is a port on the side of the vessel, underwater, that you can take in or discharge water through.
The ship’s officers use ballast while loading and unloading to maintain proper trim, list and stability. This is key in container operations as the shore cranes need the ship to be within limited tolerances of list and trim to work.
Does this answer your question?
Thank you for giving me such a comprehensive, yet easy-to-understand explanation. So in practice, would the use of ballast be of any help in refloating a vessel that has grounded and listed?
Sometimes the worst thing to do is to rush to free the vessel. But yes, sometimes all it takes is to adjust the ballast of the vessel and you’re free. It all depends on the circumstance of the grounding. Lots of variables to consider, such as speed prior to grounding, initial draft of the vessel, hull integrity (or lack thereof), state of the tide, type of bottom you’ve grounded on, severity of list, can you pump internally or externally or both.
Bunch of years ago I worked on an itty-bitty (300’) container ship running Norfolk to Iceland. We supplied the US bases, so almost always came back empty. We carried 20’ containers of sand in the holds for additional ballast.
This is why I love the gCaptain community. Any other mariner forum would have given him a hard time for posting a ballast question to the Engineer’s section 
[QUOTE=john;14265]This is why I love the gCaptain community. Any other mariner forum would have given him a hard time for posting a ballast question to the Engineer’s section ;)[/QUOTE]
Thats what I like about “new post search,” I don’t notice which forum its in!
the simple answer is ballast can be used to help refloat a stranded ship, but C_A said it well, hasty action can cause worse damage. Some have speculated that if the EXXON VALDEZ had been immediately backed off the rocks after the grounding, she could have easily capsized, with loss of life and greater pollution. (note, I just used spell check, cause I fugged up pollution and was too lazy to try to fix it, and the computer offered two options “pollution” and “solution,” hehe)