How to Fix a Kohler Toilet That Runs Constantly

A toilet that never stops running is leaking tank water into the bowl past a worn flapper, or overfilling past the fill valve setting.

Low risk — no live power or gas involved once unplugged.

Tools

Step 01
Run a dye test
Drop food coloring into the tank and wait 15 minutes without flushing. Color appearing in the bowl confirms the flapper or canister seal is leaking.
Step 02
Shut off and empty the tank
Turn the supply stop clockwise until it stops, flush to drain the tank, and sponge out the remaining water.
Step 03
Replace the seal
Unhook the old flapper or lift the canister and pull its rubber seal, then fit the matching Kohler replacement squarely on the seat.
Step 04
Set the water level
Restore water and adjust the fill valve so the level sits about one inch below the top of the overflow tube.
Step 05
Check the chain slack
Leave just a little slack in the lift chain. Too tight holds the flapper open, too loose keeps it from sealing after a flush.

A continuously running toilet can waste hundreds of gallons a day, which shows up quickly on a water bill.