There seems to be some confusion about this. Two post stated:
Put mild nitric acid (the plumbers type from the hardware store is
what I use)..." and "you meant muriatic acid, a weak form of
Both are inaccurate. Drain cleaners are of three types, Sulfuric acid
(often 90% H2SO4, basically a thickened battery acid, sometimes in
the less active NaHSO4 dry salt), Sodium Hydroxide (Lye in solid
form sometimes with aluminum shreds to cause fizzes, or in solution
at 10-30%), and enzyme or bacterial cleaners. As far as I know,
Nitric acid is NEVER used in normal pluming operations. Muriatic
acid is just a technical grade of hydrochloric acid NOT sulfuric
acid. It is sometimes used to flux, clean and tin metals for
soldering, usually combined with tin chloride. Sulfuric,
Hydrochloric, Phosphoric, Sulfamic acid and Oxalic acids among
others are used to remove hard water deposits and rust stains.
Hydrochloric (Muriatic) acid is used to adjust the pH of swimming
pools (NaHSO4 seems to be the preferred acid) and clean concrete.
As I stated in a previous post, hydrochloric acid is a nasty,
volatile acid much the same, although not quite as bad as nitric
acid, causing rust in on any unprotected steel in the vicinity. I
would stay away from it unless you have a protected, ventilated
Marlin, who has not taught chemistry class for 30 years.