We have 3 Briggs 4400 toilets, and have gradually aquired the same problem with all of them. The first thing that happened was the float-cup would not drop when the toilet was flushed. Then then tanks would not stay filled, so now you have to manually push the float cup down and wait for the tank to fill so the toilet can be flushed. The only advice we have been given was to add weight to the float cup, but when we did this, it wouldn’t come all the way back up and the tank just kept filling. We have very hard water here and we were wondering if mineral deposits could be to blame. Any advice would be helpful. Thank you.