Dangerous product. Use at own risk. I had no sink for the weekend after using Green Gobbler.
I used in my bathroom sink, which was running a bit slow. The product turned to concrete inside the pipe so no liquid of any kind would pass. I could not even snake it out myself and had to pay a plumber to come out and unclog. He almost had to take the pipe out but was just able to get it clear enough.
Worst was yet to come. I contacted customer service about it four months ago, still no reimbursement. Initial calls and emails were not answered. After a while, I received automated messages, then finally a human. I was told 2-3 weeks for a claim. When that passed, I was then told the matter had to be handled by an outside insurance agency, and these cases were impossible to prove. I'm out $160 and had to deal with the initial disaster with no help.
I can only state my experience, but it did not work, in fact, caused further problems that I never had to begin with. The company should stand behind their products and help out their customers. I was toyed with, then outright dismissed.
Bottom Line: No, I would not recommend this to a friend