what is keeping water in a bathtub
Using a Toilet Plunger. 1  1. Scrub the strainer or stopper to remove any gunk. Remove any screws securing the strainer with the proper screwdriver. 2  2. Fill the bathtub with a few inches of water. You want to fill the tub with just enough water to submerge the plunger; water is how the plunger gets suction.