I have a float-cup fill valve, Fluidmaster 400 model series. The classic solution to adjusting the water level is to turn the screw in a clockwise manner to make it go lower and counterclockwise to go higher (unless if I have reversed that).
Well, turning this screw in either direction seems to have little impact on the final water level which is above the water line. Actually if I go all the way high there is a possibility that the toilet won't stop running but I can't get the water to be anywhere near the water line on the lower end, it is always going to be above it by a bit.
So if I manually hold the, and I hope I have this term right, cylindrical plastic float in the up position the water will cut off and that is a way I can get the water to stop before it hits the water line. However, if I do not touch this cylindrical plastic float, it has trouble raising to the proper level and that is why it is late to shut off the water because the cylindrical plastic float on its own can not reach the proper height. On top of that, it looks like the cylindrical plastic float might even slip down a little bit so it has trouble maintaining its current height.
What could be causing issues with the ascension of the cylindrical plastic float and making the screw of little use to adjust the final water level?