Filling the reservoir slower can have two causes.

1. The membrane in the float valve must be replaced.
   Click here for an instruction
   
   
2. The filter in the float valve is clogged.
   Dismantle the threaded piece, take out the filter and rinse it clean. Place the filter and the threaded piece back on the float valve.
   
   
3. The supply line is clogged.
   Flush the pipe or consult a certified installer.