It would take the faucet 18 hours to fill the tank because 18/12=1.5. That means it will be 1.5 times slower to fill the tank up with the hose on. 1.5*12=18.
Logically if you double weight on something it means that you are adding the exact same weight as the first object to the same thing to make it twice the weight as the original, so yes... the weight will double if the length is doubled