The most common reason for bathroom sinks and tubs to drain slow is hair. First, remove the pop-up or stopper and try to clean out as much hair as possible, reassemble and test. Plungers are usually not very effective on bathroom sinks and tubs, as the hair clings and is not a solid mass easily pushed out of the way. For a plunger to work you will have to cover the overflow tightly of the pressure will just come out there. A small hand auger may be required. A drain cleaning chemical product such as SEPTICLEAR INC.™ HAIR AWAY may work – but be sure to read the directions prior to use. Some products are not to be used if the drain is completely blocked. If you still haven’t been able to clear the drain, you need to call your plumber.