This has been an annoying problem we've had for years, a slow draining bath tub to the point now it's a no drain bath tub. The nut at the top of the down shoot I have completely rounded not realizing it was brass and adding too much pressure. There is very little clearance and is below the floor level. My last resort is to get a small grinder and grind a slot in the nut and apply a piece of bar stock and give it to her. I have my droughts whether it is going to release. I have a sink that drains into the down shoot just a little below and it drains well so the problem I see is a blockage at the end of the pipe that enters the down shoot. My question is what can I put down the pipe that will work around the 90 degrees and get threw the maybe rust build up at the end. Any suggestions please.