I have been using the bleach treatment on my drains for years. The
only damage is that it gradually wore off the shiny chrome surface of
the bathtub drain, and left the dull brass underneath. No big deal to
me. On the sink drains I wipe off the chrome darin ring afterr pouring
the bleach downt he drain, and careful not to splash! (as withness the
****e spots on a blue shirt