Here's another one I've seen online in several places which I decided to try after wasting money on expensive drain opening products. I'm not sure why it works so well, but it does. Perhaps the rapid expansion combined with the acidity is the explanation. If your problem is something other than hair and soap scum I can't say it will work, but this preparation got rid of two slow tub/shower drains for me, cutting right through the gunk just like that. No more toes soaking in a puddle!
Drain Opener
1 cup baking soda
1 cup white vinegar
Remove whatever cover/plug is over your drain. Spoon in 1 cup of baking soda, and dump the excess over the hole. Cover with an inverted Pyrex 2-cup measuring cup. Slowly pour 1 cup vinegar into the hole, slightly lifting one edge of the Pyrex by the handle as you do. It'll bubble up all over the place, but it will drain back down, so don't pause. Let stand at least thirty minutes and flush with a liberal amount of hot water.
