I think that stuff is close to pure lye in liquid form. My sister and brother in law have a old home and a cup or so of that stuff down the shower drain once a month keeps it nice and clean. I had something stuck in one of my drains once and a couple doses of it clear it right out. For some reason I suspected it was either a bunch of lint or a sock that had got sucked through the washer drain.This stuff... dont spill it, and a little goes a very long ways:
Instant Power Hair and Grease Drain Opener is the solution to the most common drain stoppages. It utilizes a strong, non-acid formula that dissolves hair and creates heat to melt grease. Safe for all pipes and septic systems.www.homedepot.com
Lowe's sell a product that is similar, just a smaller bottle. If you go looking for it don't look on a shelf, I have always found it on the floor.