Karl Townsend wrote:

It works on the odorant (I said to use it, pH adjusted etc) but *not* if
the odorant is trapped in grease/goo/crud. You need something else to
mechanically bust that up and out.


Looks like Richard has a point on this job. I soaked the tank in a strong
shot of bleach full of water overnight. Its no better this A.M. Looks like
my plans to use this tank in the house are off till spring. I'll leave it
outside all winter. Maybe time is the cure.


It isn't bleach diluted by water, Karl. It's a strong shot of bleach by itself,
swirled around to coat the whole inside (for a big tank like that maybe 3-4
cups) followed by a hot water rinse (not cold). Worked for me, anyway.

But I agree, Richard may have something there.

I've had an idea for a long time about the inside of propane cylinders. If
you filled the cylinder with an ionic solution (e.g. water & washing soda or
lye) and suspended a cylindrical electrode (sheet lead rolled around a dowel?)
straight down from the valve opening so it didn't touch the cylinder anywhere,
then put DC voltage between the tank and the electrode, I wonder if you could
derust the inside. Or blow off most of that black crud anyway.

Worth a try, anyway. You'd need quite a bit of amperage, probably have to use a
MIG welder for the power source. Tank would be negative, electrode positive.

Grant Erwin