Is Drano bad for your plumbing?
Drano® will not damage pipes or plumbing. Drano® products are powerful enough to dissolve nasty clogs, but they will not harm your plastic or metal pipes, so there's no need to worry. ... All Drano® products are safe and can be used with plastic pipes or metal pipes.
Why you should never use Drano?
Because of its corrosive nature, Drano can cause toilet bowls to crack, PVC pipes to melt or break and the glue that holds pipes together can be eaten away. If any of these things happen, you're going to be left with an inoperable plumbing system and costly repairs.