Thanks Jadnashua and Terry! As i posted 1.5 yrs ago in this thread (as deanalt, not deana), my plumber did use that very 1-B1-x valve but, during installation, even with the new flapper, which is roundish not flat where it seals by the way, he could never get the toilet to shutoff. Eventually, after two return visits, the plumber simply lost interest and blamed the bad design of the Rialto and/or the tube/seat where the flapper sits as maybe being uneven. I don't recall if, at the time, Kohler had no replacement for that seat or just that it seemed like a major job and my plumber couldn't promise me anything would help, but we didn't try to replace it! To the extent it is leaking, it is NOT leaking outside the toilet (thank god, because the bathroom has padding and carpet!).
Although I do know we have hard water, I have no reason to assume the valve is not working correctly. Occasionally, I do see water dripping out of the top of the valve while the tank is filling and am not sure if this is bad or intended. I could take it apart and recheck it, if that seems to be worth doing. In fact, I would love (no pun intended, Terry) if someone, looking at that photo, would tell me what all the screws (including the horizontal plastic bolt on the side) on that valve are for. At times, the toilet never shuts off and it is hard for me to fathom that the flapper seal is that bad. There must be something about the design of the valve adjustment arm that prevents it from fully shutting off, even if for just a few seconds. I try bending the arm, etc, and nothing seems to help! Clearly, i don't really know what I am doing. I never had these kinds of problems with my older toilets, and I am 57 years old! Sorry for the stream of consciousness!
That said, it sounds like the problem is in the flapper area. Maybe it was just poor quality control as jadnashua suggests (although I do recall switching it out with a used flapper from another same model toilet we have and that not helping, but maybe not). I seem to recall taking the new flapper back to the store and getting a replacement but am not sure (probably I just returned the valve). If so, the new flapper was no better. Ultimately, someone advised a thin coat of vaseline for a couple of weeks and that did, after a day or two, work. But the hissing eventually returned several times and each time, a little more vaseline eventually stopped it. But I do recall being told that was a bad long term solution and so, after 1.5 years of having vaseline on it, I can believe that the flapper is no good anymore. So, I will try a new one. Is any brand better than another for this specific model toilet?
By the way, the level of the water is not too high, in fact, it is decidedly low since, if it got too high, it seemed to cause even more of the incessant siphoning action back and forth. I was always confused by the bowl wash design, as to whether I could not allow the water level to reach where it seemed to be open procelain, so I kept the water level low. Once again, this toilet is beyond me, but I think Terry said it is a great design for a second floor installation and it is color matched to the sink and bathtub and pretty to boot, plus low flush, which is important here in thirsty Los Angeles.
All comments (including calling me an idiot) are welcome!
Thanks
Dean