29 January 2011
The chain connecting to the flapper should have about an inch of play. You want the flapper to open wide enough to float a few moments before it falls back down and closes off the flush valve. If the flapper is working properly, check that the holes under the rim are not clogged.
If you live in an area with very hard water, calcium may build up in the drain holes under the bowl rim. A partially clogged rim might not allow enough water through the rim to start the vortex motion and slow the evacuation process. Use a stiff toilet brush and a vinegar solution to help remove the calcium buildup under the rim.
Lastly, and as common as the poorly adjusted flapper, is an item lodged in the toilet trap. The items we find most often are small toys, rags, etc. Use a toilet auger to push your way through the trap and clear or pull back any obstructions. A toilet auger is a special tool that has an offset hand crank, a long sleeve handle and a special auger bit at the end to break through a clog or retrieve an obstruction.
The auger bit is connected via a flexible shaft to a crank handle that you control. Its reach is about three feet. The auger can be found at any hardware store.