Best/Quickest way to drain hot water lines from tank?
If you turn the supply of water to the water heater off you don't need to drain it , with the supply off you do want to turn the gas valve to pilot or off depending on the type of tank some have electric ignightors and don't have a standing pilot. The tank will be fine. After that I open the lowest taps in the home usually a bathtub if single level then the taps you want to change and the water in the pipes drain down to this level, a hose bib outside many times is at the lowest position for cold water. Now that you have the lines open would be a great time to add shutoffs to this fixture when installing the new faucet.