My roommate failed to read the instructions on the “Crystal Draino” bottle. Instead of putting 1 tablespoon down the shower drain and flushing with water, she poured half the bottle down the drain and let it set overnight. It has now set-up like concrete and I have attempted to “chisel” some of it out. This is not working and the shower is beginning to back up. What (if anything) will dissolve draino? What can I do?