The Kohler canister-type flush valve gasket seal is replaced like this:
- Flush the toilet and turn off the water supply.
- Push down and turn the guide post at the center of the canister 1/4 turn in counter-clockwise direction to separate the canister.
- Remove it from the tank.
- Pull the gasket from the bottom of the canister and replace it with a new one.
- Reinstall the canister by inserting the guide post, and lock it with ¼ turn in clockwise direction.