The number one problem with a slow bathtub drain is hair. To remove hair from a bathtub drain, a drain tool like The Drain Claw does the job with a simple push and twist.
The average person loses about 100 hairs a day. This hair gets caught at the crossbars of the bathtub and builds up until it slows or clogs the drain. If you use a tool like The Drain Claw every month, you can keep this hair from going further down the drain where you would need drain chemicals.