In most bathtubs the overflow drain is located near or just below the taps. The drain usually connects to the drain at the base of the bathtub. Together the pipes linking the two drains form an L shape. You will need a tub drain remover (available at most hardware stores) to remove the drain casing. If the brackets or crosshairs of the drain are broken you will need a drain key to remove the casing. These keys are ideal and fit into almost all sizes of drains. Generally side drains are easier to remove unless the taps overlap the drain opening. In this later case you will be forced to remove the taps before the drain can be accessed. Since the safety drains are only meant to act as a safety overflow feature they lack intricate filters.