I poured this drain product into standing water to clear a clog in my 1920s bathroom sink. I let it sit overnight to dissolve the clog. Nothing on the bottle suggested, much less warned that the product was not safe for enamel surfaces. After I got the plumber out to snake the drain (since the product didn't clear the clog), I discovered that this product had eaten away the enamel. Now the finish on my sink has been eaten away and has been replaced by grooves, as if I'd sandblasted it. I've used other drain products, like Liquid Plummr and Drain-O, without any damage to enamel before. I called the James Stephens Corporation to complain. All I was asking for was a refund. But the rep I spoke with didn't agree to give me a refund, and he told me a manager would call me the next day to talk to me about it. Of course, I never received a phone call or a letter. I've taken photos of the sink and I am going to send them to the company and ask that refund me for the product AND that they pay the $175 it will cost me to get the enamel resurfaced.