Either waterproof pipes (Golden would be better) or Liquiducts. Just attach it to the valve block on the tank and pump it out. For waterproof pipes you need to use a wooden waterproof pipe and a redstone engine (or autarchic (sp?) gate, but I doubt you can get them at this point), for liquiducts you need to switch the pipe to extract move (right click with a BC wrench) and apply a redstone signal.