How do I clean the drain in my bathroom?
I use "Zep Crystal Heat" drain opener that I buy from Home Depot or Lowes. It contains sodium hydroxide so wear protective gloves, eye wear and do not breathe the vapors. Read the label and follow their directions. I usually double or triple the amount they say to use. First, remove the drain cover, then  run the hot water to get the standing drain water hot which makes the product more aggressive, open a window in the room, pour in the stuff, turn on the vent fan and get out of the room. To check on the progress, I hold my breathe, walk into the area, check and get back out. When the vapors stop, I re-enter the room, turn on the water to flush the drain and "shazam" the drain is clean. This works for me.