question

I am replacing the water lines to my water heater. Do I have to turn it off and drain it to replace the lines?

Not necessarily...but you have to lower the level of water so that it doesn't get all over the place. I think I would turn it off for safety and if electric to prevent the possiblity of burning out an element...then don't turn it back on until sure the tank is filled.

If its a top feed heater (both water lines connect to the top of the heater), just turn off the gas or electric as the case may be, shut off the water, and open a faucet to relieve the pressure. If its a side feed model with one line at the top and one line on the bottom (both on the side) then yea youll have to drain it.