If your toilet has a water port in the bottom of the bowl (opposite to the outlet, about the size of a quarter), follow these instructions...
1. Using a cup, bail out the bowl until almost empty.
2. Pour in enough household vinegar to cover the small hole, (about a quart).
3. Let stand 3-4 hours.
4. Use a piece of coat hanger wire to clean out the port.
5. Flush and repeat, if port is very clogged.
Frustrated by Plumbers, April 2007