The fill valve on my new toilet guts shuts off instantly if the water supply knob is turned on all the way. FYI my knob only turns a quarter turn to have the water on all the way.
It literally shuts off within one second of flushing and obviously no water fills the tank.
I have to shut the water supply valve under the toilet off and back on part way to get the toilet to fill. When the water shuts off I also get the hammer sound. I have tried two different fill valves in two days and the same thing occurs with both.
The modern style float is not even touching the water as the toilet might get 100 ml
The type of valve is the kind with no ball float, its the new style