Can you unstop a drain with muriatic acid?

Muriatic acid or hydrochloric acid (HCl) will not harm copper pipes. I am a licensed Heating& cooling technician and I use Muriatic acid all the time to clean out hot water tankless coils and boiler hot water coils and I have seen it used to clean out hot water copper piping in houses to remove scale and

mineral deposits. I use a 1/6 Submersible pump that i purchased at Home Depot. It's not a chemical pump and I have used this pump over 4 years and i have ran Muriatic acid through it at least 60 times and the pump still works great. I even took the pump apart to see if any damage was happening to it and it looked just like new. just wear long rubber gloves and full goggles for your eyes. safety glasses will not protect your eyes. the acid can splash up under the safety glasses. If you get any on your skin just rinse it off with cold water. Muriatic acid or HCl cleans up really well with water.