Any resin in the house?
Any chance that there has been a crack in the brine line? Getting air into the system while in brine draw?
Air would be one of the first things that I would be looking for in getting into the systeme.. either from the brine tank or from the well..
There are a few other reasons, distributor tube could be cracked below the resin level and getting pushed out while in rapid rinse. really high pressure... say 90PSI...
There are 3 items for the media tank... the tank, resin(some gravel) and the distributor tube that goes from valve to bottom of media tank ..
The room between the top of the tank and the resin for the culligan should be about 16", with you getting to see through the tank, take a reading and find out how many inchs you come up with..
Until we get a handle on the resin getting out..