Rainsoft system not using salt

I moved into a house with a rainsoft water softening system. I went to add salt and saw that there was some in there. I decided to wait untill it needed more, noticed hard water stains in the house. Checked the salt, it used none, but goes through the cycles every day. The model # is hard to read, but looks like LMB 1135 .6T6? Serial # 226045, manufacture date 6-29-2000.