We had a HydroRight in the toilet for several years (with the split, dual flush handle) and all of a sudden, water began trickling into the bowl, and the tank would refill every 10-15 minutes, which would take just a few seconds.
I thought maybe there was a rebuild kit for the HydroRight so I could replace some seals, but didn't find one. So, instead I bought all new internals, but this time a Fluidmaster Dual Flush. This one came with the angled adapter to change the bottom mounting point of the overflow tube from an angle to being level, onto which the complex flushing mechanism fit.
The toilet still had the same problem. It seemed to me that the leak must have been where the flushing mechanism attaches to bottom of the overflow tube. The new one attached via what I believe is plumber's putty. I thought maybe I hadn't cleaned the ring adequately where contact occurs or maybe didn't dry it well enough, so I took it apart, and threw away the putty that came with the Fluidmaster. I bought new plumber's putty (which is a very different consistency from what came on the Fluidmaster adapter), rolled it out, and, after cleaning the adapter and the contact point at the bottom (where the flapper would normally touch) very thoroughly and letting them dry, applied the putty to the adapter, then pushed it firmly into place. Then, I shoved the Fluidmaster flushing mechanism back into place on top of that adapter.
Just to be clear, when I cleaned the contact point at the bottom of the overflow tube, I observed that it appeared to be smooth, undamaged, and in perfect shape. I would've expected a good seal.
Still leaks. No idea what to try next. Suggestions?