I have a leak close to the water shut off under the bathroom vanity. I am trying to replace the pipe leaking but there is still some water dripping out of the line and cannot stop it. Piece of bread didn't work, it will not hold enough time for me to make the repair. Would I have to actually drain the hot water tank. That would be a thought I had but is it necessary?
Sometimes draining just a few inches of water from the tank will provide enough relief in pressure to stop the dripping, if it is indeed siphoning back from the tank. It's also possible that you just need to wait a bit longer for all the water to drip out. Opening all the other faucet valves and flushing the toilets with the water off will also help drain the system.
I would avoid the bread if you can, though it will flush though the pipes OK, it will gum up all your aerators and valves.
If you do need to work on a pipe with water in, they sell Pipe Freezing kits which you apply upstream of the work area. These will give you 15-30min to work on the pipe while the ice block you created melts.