I have a Pegasus dual-flush toilet that was installed new approximately a decade ago. I just moved back into the house last September after renting for several years. Every once in a while the toilet won't flush properly. The water level in the tank will go down but none of the water in the bowl gets flushed. I don't have a water softener so I suspect the problem could be due to calcium/lime buildup in the valve(?) Or, perhaps the valve mechanism just wears out over time and needs to be replaced; I don't know. Regardless, does anyone know what could be causing the issue and what would be the easiest way to fix it (short of replacing the toilet itself)? I also don't know if this is the old style valve or the new one; I'm sure a professional plumber could tell. TIA.