Toto CST854 tank does not hold water with replaced flapper and water supply shut off

[ERT1900]

Recently changed my toilet flapper with an OEM replacement for the Toto CST854.

After changing the flapper and shutting off the water to the toilet, the tank drain in an hour. Running my finger along the seat for the flapper indicated with the blue arrow, I could feel deposits on the lip. I used a rag to clean up and now after shutting off the tank, it drains in 24 hours.

With the toilet being discontinued, I have not had luck finding a replacement toilet valve seat assembly. Recommendations on next steps?

 

[TJRAD]

Toto CST854 "ultimate" 1pc toilet....
Replace the flush valve with the new tower flush valve. part # is.....(THU460-15E-A).
Its an easy replacement because you have a 1pc toilet (Just 3 screws)..
The Toto Ultimate, at the time was a good toilet but the flush on the new toto's are much better. Consider Changing to the Toto Ultramax II for a superior flush.
Good Luck.

 

[Sponsor]

 

[ERT1900]

Toto CST854 "ultimate" 1pc toilet....
Replace the flush valve with the new tower flush valve. part # is.....(THU460-15E-A).
Its an easy replacement because you have a 1pc toilet (Just 3 screws)..
The Toto Ultimate, at the time was a good toilet but the flush on the new toto's are much better. Consider Changing to the Toto Ultramax II for a superior flush.
Good Luck.
View attachment 106473

Thanks for the feedback. UPDATE: I spoke with TotoUSA a couple of days ago and they recommended the THU831-A assembly for my model very similar to pictured above. Swapped out in 5 minutes, very easy and back up running.