All are saying that "I" can get it from the tap to do something, and the something is what differs between each of the statements. For the first statement, "you" are saved pumping. That is, "I" get "you" a discount of some sort on pumping (which somewhat makes sense for gas). The second, or B, says that the action of getting it from the tap makes "you" not have to pump any more. It saves "you" the effort of pumping. The third just makes no sense and is wrong, as [Catija][1] says.


  [1]: https://ell.stackexchange.com/users/16318/catija