Troubleshooting & Repairing Kohler One Piece Toilets is not the easiest task to do. Kohler has utilized so many proprietary parts that just getting parts can be a huge headache. Even Kohler distributors will not have many of the parts in stock and ordering direct from Kohler is often the best option with a 3-week back order being the norm.
The Kohler One Piece Toilets such as the Gabrielle, Santa Rosa, and San Martine, have some models that aren’t too bad using a standard fill valve and a proprietary flush valve and flapper. The flapper is more commonly available and even has aftermarket replacements leaving only the flush valve as a problem to get. Toilets such has the Pillow Talk, Palarre, San Raphael, Rochelle, Rialto, Cabernet, San Miguel, and Rosario, become more of a problem using proprietary fill valves, and flush valves making any thing more than a flapper replacement a headache. Still others such as the Rochelle K-3385-EB, Champlain, Pompton, Placid, and Trocadero & San Raphael Power Lite Models, are even worse with complex and expensive proprietary parts often costing more than a new toilet would.
The basic troubleshooting is just like any other toilet with the concerns whether the fill valve is filling the tank to the proper level, fully shutting off when the proper level is reached, and not leaking spraying water everywhere. The other concern is whether the flapper is sealing correctly or, needs replacement and the operation of the handle and flapper chain adjustment. The flush valve sealing to the tank is often problematic especially with the plastic flush valves that use locking tabs to secure them in place and compress the seal, this design is weak and often leaks water from the tank into the bowl. The biggest concern is the expensive and complex fill valve/flush valve combination mechanisms that can be rebuilt but are complex enough to even scare away many plumbers.
For many of these toilets replacement is the best option.