Paul,
Your system is toast.
There are no replacement parts for them.
Mixing the tank and bowl is not a good idea either.
You did get 10 years of use though.

: I have had 2 od these 811000 tanks in the house for 11 years w/o problems. Now, however, one of them no longer flushes with the same amount of pressure as the other one, which still flushes great. The poor flush takes a full 3 secs. from the time the flush handle is activated until the cycle ends and re-pressurizing of the tank begins. By comparison, the one that works great takes 7 sec. for the entire cycle to complete. Thus, the 3 sec. cycle results in several flushes to fully discharge wastes.

: I have read all about this model's problems and wonder if I can just purchase the tank and pressure tank assembly, leaving the bowl/seat in place. My toilets are the Kohler Wellsworth models and I see that these same models now contain a different pressure flush system ("Flushmate") than the 81100 tanks.

: Any ideas on whether I have to purchase the entire Wellsworth (toilet & tank assembly) with the new system or can I simply change out the tank and flush assembly?

: Thanks for any guidance.