Hello: In order to adjust the water level in the toilet tank what needs to be done? I think item 1 (a piece of plastic that juts out) and item 2 (a screw) in the picture are relevant here. When the tank refills, should water be flowing through the tubes labeled 3 and 4. In this instance, water does not flow through the tube connected to the overflow pipe (#4); however, the water level in the toilet bowl is normal? How does that happen? If there is no leak at the base of the fill valve assembly (#5), and the tank empties with the shutoff valve closed, does that mean the flapper (#6) needs to be changed? If water leaks through the base of the fill valve assembly (#5), can it be fixed by loosening and retightening the nut underneath or do I need to purchase a new fill valve assembly? I noticed a leak after the fill valve unit was jostled around a bit. Thank you so much!