Disconnect plumbing begin by turning off the hot and cold water shut off valves that are located beneath the sink.
Removing bathroom sink from wall.
Place a small bucket on the floor beneath the water valves to catch any water left in the lines then disconnect.
And water cut off valves are on the hot and cold water lines coming out of the wall.
Then you can disconnect all the plumbing below your sink.
Loosen the p trap.
Turn off the water supply to the fixture at the two small water valves mounted on the wall beneath the sink.
Then place a bucket under the sink to catch any water remaining in the pipes as you disconnect them.
If you want to remove the wall behind a bathroom sink but you plan to leave an existing commode or tub shower in place you must make provisions to vent those fixtures.
Turn the water cut off valves under the sink.
How to remove a wall mounted bathroom sinks.
In a typical bathroom.