Many people may try to band aid the problem by recaulking the edges of the sink backing to the wall.
Fixing bathroom sink to wall.
For a slip joint leak first tighten the slip nut.
Now that you have made the repair to the water damaged bathroom wall all that remains is to finish off.
Fill the sink bowls then as they drain check all joints from the sink to the wall with a dry tissue see photo above.
Wall mounted sinks have a great modern look and make a small bathroom especially a guest bathroom seem less cluttered and more spacious fortunately mounting a wall sink is a doable project for most diyers.
How to fix it.
They may be loose because the screws lifted the cabinet slightly.
The problem is the wall is plasterboad and the fixings supplied are for a solid wall.
Drill the holes with a 5mm wood bit.
Finally cut and install new base trim before applying silicone to the inside edge where the drywall and tub meet to create a watertight seal.
The wall is plasterboard and the sink is fairly heavy it also is the freestanding type ie the pedestal is not to the floor.
If so replace them with slightly thicker ones that you have to tap in with a hammer.
Insert wurly fixings into the holes these are known as metal plasterboard fixings at the builders merchants.
Run and drain the dishwasher and check the waste hose connection.
Offer the sink up to the line and get someone to mark the screw holes through the sink which can be found at the bottom.
Squirt white silicone onto the back of the sink and place onto wall.
Drive the screws into the new holes and sink them into the wall studs as far as they ll go without over tightening them.
Check the shims after refastening the cabinet to the wall.
As with any heavy object attached to a wall over time a sink can become loosened from its anchored state on a bathroom wall or under a kitchen cabinet for example.