Good you should not use the acid openers.Since I am not a fan of harsh lye based cleaners, I think I will look for a more environmentally and wallet friendly solution to maintain my drains. Perhaps the baking soda and vinegar solution might suit me best. Anyone have success with this for maintaining clean and free-flowing drains?
I have been told from many customers that the baking soda and vinegar trick works great, but then again I'm a drain cleaner so I'm drain cleaning the drains they use it on. I would keep a cheap snake on hand and shoot it down your drains every 6months or so.
The real problem you have is your bath sink drain is copper and your main stack is cast iron. these two metals will rot each other. The 1 1/2" drain is most likely down to less than 1" . Nothing eats this not even the acid openers. Yes the snake is a real pain but it is the only thing that will keep your drains working fast, aside from replacing the copper to plastic.