If you have a Kohler toilet in your home, it’s likely that it makes a “clank” sound when you flush it.

According to two professional plumbers and Kohler tech support, this is normal. (Unbelievably.)

Kohler's toilets have a proprietary flush mechanism that uses a cylindrical riser, instead of a lever, to actuate the valve that controls the flow of water.

The clank is caused by the cylinder hitting the underside of the tank cover. (You can confirm this by removing the tank cover and flushing. If the noise is gone, you found the problem.)

The fix is to put a couple of very thin rubber feet under the tank lid to raise it. The tolerances are very tight — it won’t take much to move the lid out of the way. Try something like this.

To be more specific and to help the findability of this tip, the toilet I have is a Kohler San Raphael 1.28 GPF Elongated One-Piece Toilet. Part number 1126374. Model 3722

You’re welcome.