> According to girl friend soda (soda ash) (Na2CO3) should do the trick, hot
> water will speed it up.
>
> It is commercially sold as calc-remover (brand: Calgon here in Turkey).


Haluk,
thanks for the hint!
I remember Calgon when I used to live in Germany... but it was to prevent
calcination. You needed to add it together with the detergent. I used it for
the washing machine and the dishwasher (now my wife has a human one... me!).
Later: Found on the Internet

RE: Coffee pot decalcifying
  a.. Posted by: hare_ball_rabbit (My Page) on Tue, Feb 5, 02 at 9:42

      If you can't stand the smell of vinegar, use Arm and Hammer Washing
Soda. (sold in the laundry isle)
      I bought an 8 oz jar of Brew Rite brand automatic coffee pot cleaner.
Upon getting it home, I read the only ingredient on the jar. SODIUM
CARBONATE. I looked it up on the net, and much to my suprise found out it
was nothing but washing soda.
      Pure sodium carbonate is a white, odorless powder that absorbs
moisture from the air, has an alkaline taste, and forms a strongly alkaline
water solution. It is one of the most basic chemicals, commonly called sal
soda or washing soda.

      You can buy a huge box of A&H washing soda for the same price I paid
for my little jar.
      :(
      How dumb did I feel? Now I refill my little jar from my box of Washing
Soda.

      DIRECTIONS FOR USE (off the Brew Rite jar)

      1 tablespoon to 4 cups of water

      Fill pot with cool water.
      Add soda and mix until dissolved.
      Pour into reservoir, brew and discard.
      TO RINSE, brew full pot of fresh water thru machine two times.
      Rinse brew pot and funnel. Ready for use.
      Repeat every 2-4 weeks, or as needed.

      Soaking your brew pot in the solution for 5 - 10 minutes will remove
hard water deposits.