 So my recommendation would be to call a different kind of professional, not a plumber, but someone that specializes in drain cleaning and has a good reputation for being able to make that particular type of repair. I think that's going to be the easiest way for you to get to the bottom of it. I would not recommend any type of additive to that drain to try to clear it in these liquid products that clear drains because they can be very, very corrosive. Mary, good luck with that project. Thanks so much for calling us at 888-MONEYPIT.