It was installed originally by Culligan about six year ago when the original owner of the home had the Culligan installed by the builder. It has not been an issue, but I always thought is seems a "substandard" installation.
This drain line has become a real PITA. The existing Culligan uses a 5/8" INSIDE diameter clear plastic tube that connects to some some type of plastic nipple that is screwed into the copper fitting that was sweated to the 1/2" copper pipe (the last picture that Tom commented on) that goes to the drain in the laundry room and then connects to the Culligan.
The new 7000SXT came with a barbed plastic adapter to convert the 7000SXT to a 1/2" tubing connection. Obviously the 5/8" ID diameter clear plastic tubing that is connected to the pipe is not going to work to connect to the 7000SXT. I was HOPING to avoid pulling off the 5/8" ID clear plastic tubing from the wall connection because I can seem to pull it off and I will have to cut it, since I don't seem to have a choice. I would think I could buy some brass fitting to screw into the copper fitting that was sweated to the copper pipe, and then connect the 1/2" tubing from the new 7000SXT. The supplier of the new 7000SXT included black plastic 1/2" tubing, but it does seem cheap compared to the much much heavier clear plastic that Culligan used. It probably doesn't matter much I guess since this line is not under permanent pressure.
Just for my info, how are you SUPPPOSED to connect a water softener to a 1/2" copper line that comes from the wall. Culligan installed all (well I have seen three) softeners like this in my community (they partnered with the original builder to rip people off and install the Culligans as part of the sale price of the homes).