Lindsay water softener

I have a Lindsay ecodyne model 20114.12 water softener. For the last month or so I have had greatly reduced water flow in the house. I replaced the filter. No effect. I took filter back out and turned on the water through the softener-it barely trickles out. When I press the "bypass valve" I get 4-5 times the flow from faucet (hard water) It doesn't seem like it is using much salt either. Does this unit have a backwash function?