How do I unclog tub drain full of drywall plaster.?
The drain cap probably has a set screw underneath. You can use a compact mirror to find it. It will need to come off. You can use a wet/dry vacuum to get the loose chunks out. You need to use a sink snake to break up more, and then vacuum again. If that is still not enough, then you need acid type drain opener. You will need a full face shield, rubber gauntlet gloves, heavy clothing that covers all of your skin and a clear escape path, since this is very powerful and dangerous. Do not be stingy with the safety equipment. Do not breath the fumes. This gets really hot so should not be used if there are plastic pipes. Better yet hire someone else to do it.
