Okay - this is less of a question, then an opportunity for discussion.

Got a call. Current client put something down her disposal (corn starch) and it solidified.

Yep.

So, she calls plumbing company. Someone (most likely NOT the actual plumber) tells her to use acid to clear it out. REALLY!

First. I have heard and dealt with this before, but it just erks me to hear people at the hardware store, and stories like this. I never tell anyone to use anything like this for two reasons.

1st - I like mechanically removing clogs of obvious reasons, but I know how to.
2nd - You can't count on the average user knowing how to use chemicals properly anyway.
Safety, safety.

I tend to lean hard away from drain cleaners too. I have gone out of my way to spend time teaching people how to clear traps so that they feel confident in doing so and I preach a little about way using drain cleaners and other harsh chemicals are not so good.
But... there are far too many people who just don't understand, or have the time and understanding of why not to and often get "why would they sell it if it didn't work, or would be bad" kind of response.

The new client now needs a new sink, new pipes, and so on. No new disposal. Let's just say it's easier not to have to tell someone what not to use down the disposal, and after that one "acid" mistake - there is no money left anyway.

I just keep getting these. So - chime in and give your dimes worth.

I can not advise against using muratic acid, or any acid, in a enclosed area such as a rest room strongly enough. As a young boy I would take limed up toilet bowls out in the alley behind the shop and boil the lime out of them. Over half a century later my lungs still carry the scar tissue that the acid fumes caused. A few years ago I lost a good friend when he used a commercial drain cleaner containing sulfuric acid in a unvented bathroom. Acid IS NOT A GOOD IDEA to use to clear mineral buildup. Take it from one who's paid the price.
As a repair plumber I have never recommended using harsh chemicals. In your drainage system. Besides they only seem to work in TV commercials and when you try to remove the water you could burn your hands or damage your eyes. I prefer to snake a drain line instead of depending on a drain cleaner. Regards, Tom

It's good to know Tom that I am not the only one who feels this way. I cannot use bleach myself, but I use vinager/water and baking soda for preventive measures in the shower drain. Then boiling water if needed.

I try to instill this with my friends and anyone who wants this knowledge. I still remember renting below someone who used acid on their pipes. I was not home for the weekend, but I did get a frantic phone call. "I DO NOT WORK ON ANYTHING that someone has used this product. Never have and still won't.

I have 3 girlfriends who now know how to clear their drains without using harsh chemicals and they know what a trap is and how to take it off and clear those too. So - I am making some headway. They also know I won't work on anything after they used something harsh for awhile.