Re: chlorine hardening rubber
I first learned of this problem many years ago from a plumber in SoCal. He said the highly-chlorinated water routinely hardened gaskets and rubber toilet flappers, a fact that was quite lucrative to plumbers.
The product info for Liquid-PlumrŽ clog remover indicates the primary ingredient is bleach (sodium hypochlorite) and in their own words, "we do not recommend using drain openers in rubber pipes. The products may damage rubber."
Looking online, [url=www.omegachem.com.au/docs/mega_handbook.pdf]this .pdf[/url] has a section (4.2.4 - Rubber Lined Steel) on how steel tanks lined with rubber deteriorate in as little as 3 years and have to be completely replaced after ongoing exposure to bleach.
Mind you, I'm talking plain rubber, not specially made rubbers that are designed to contain or resist certain materials.
Sue