My bathtub will not drain.I believe it is the pop up valve that does not work, I tried moving the handle up and down but the water does not drain out. The shower drain in the adjoining bathroom works fine so I dont think it is a drain stoppage problem.I have a system where their is two faucets and a third faucet for turning the shower on and a little handle that is supposed to open and close the bathtub drain.I think that is the part that doesnt work, how can I fix the pop up drain or at least disconnect it and then use an old fashioned rubber stopper. Any help will be greatly appreciated..Very Respectfully R F Driscoll