On 1/20/2011 12:32 PM, Joe wrote:
On Jan 20, 10:51 am, Molly wrote:

snip

Pour some cheap vinegar down the overflow tube in the tank and let it
sit for a few hours.

Beter yet, some dilute muriatic acid and let it sit for a few minutes.
If that is too scary, oxalic acid as found in old fashioned radiator
flush at your auto parts store, will do a bang up job in probably 10
minutes. Rinse well and enjoy.
Years ago a product called Sani-Flush was in all the stores. It used
the moderately aggressive sulfamic acid as the motivator. Such
products may still be found at a janitorial supply store. IIRC, they
did a good job on all the toilet crud of the day.

I still use Sani Flush, I find it at the local Wal mart.