A wet vac should help. Plug the overflow on the tub, and vacuum from the drain.
Our bathroom tub has an old drum trap in the floor that serves the tub and bathroom sink. Our home was built in the 1920s and the trap is probably the original. We are constantly having trouble with slow drainage. Drain cleaners provide some relief but only temporarily. Access to the trap is through a small hole which was drilled by a plumber since he was unable to access the top of the trap. It serves as access for a snake but is not convient.
Is there a better to way to clean it out, or even better, is there a replacement part that I can install.
Can you actually see two drains going through the trap?
Is it a cast iron drum trap or a second story cast iron p-trap?
How do you know that both drains go through the one trap if you can't see more than a small hole in the floor?