Softener installed Nov. 14, 2008 and seems to be still working well. I recently noticed that during regeneration, when the Performa valve leaves cycle C4(System Pause) and while in between and going into C5(Fast Rinse Cycle 1) there is a loud, aggressive copper water pipe hammering. I do not know when this started or how long it has been happening because until recently I worked a lot during the scheduled 1AM regeneration. I also noticed that the water level in the salt tank is just barely even with the level of the salt, which I keep only about one third full so if I need to move it, I can. Is this water level correct? What can I do about the water hammering? The softener is a GE with a 762 control valve. Any advice would be greatly appreciated.