fourth year
The only way to get the water out of that pipe is to turn off the water to the house, open a lavatory faucet it the same room and then open the shower valve so the water will drain out of the riser pipe into the lavatory. This assumes the lavatory is on the same wall as the shower valve, or the piping comes from the floor. It the pipe goes overhead between the shower and the lavatory, then the water will still not drain out.
