How To Adjust the Flush Handle Linkage
When a toilet's flush is too short or the toilet runs continuously, the problem may be with the flush handle linkage. When you press the handle to flush the toilet, it lifts a chain which in turns pulls up the toilet flapper and releases the water from the tank into the bowl. If that linkage is too long or too short, it can cause a problem.
Pressing the flush handle lifts the chain. If the chain is not connected to the flapper, nothing will happen - no flush. If the chain is too long, it may lift the flapper, but the rushing water quickly pulls it closed again resulting in too short of a flush. This can cause the toilet bowl not to fully empty or fully clear.
Another problem with a chain that is too long is that it may get caught under the flapper, preventing the flapper from sealing tightly. If the chain gets under the flapper, water will run out of the tank continuously and cause the fill valve to periodically or continuously fill the tank. In this case, even if the chain is adjusted properly, an excess length of chain may be going under the flapper and should be cut off.
If the flush linkage is too short, it may prevent the flapper from falling fully into the flapper valve and thus failing to seal the flow of water.
The linkage between the end of the flush handle lever and flapper should have a small amount slack in it. Don't set it tight and don't allow long segments of excess chain. Attach the chain to the flapper so that chain drapes a little bit, but not so much that it can lay on top of the flapper or bottom of the tank.