No water treatment systems. I was all through the attic. A complex attic due to it being one condo in a series of three and all two story. All other drains such as air handler,water heater,washer pan were accounted for. Did not go on the roof as it was really high and tiles. Maybe something up there has a drain piped through. So it was noted in the report and the new owner will watch it to see what it does and go from there. Thanks for all the input we really did exhuast all obvious reasons for the drain. Will keep researching and follow up with homeowner at a later date.
The setup not so much the date. As one person said maybe the handler was once in the attic. This did not appear to be the case. So yes the air handler is original and located in same spot as when the contractor put it there.
It is for a water softer. All other drain lines are min. 3/4". I see in when the garage is near to the laundry room. But it should not going to or from the attic.
There may not have been a water softener installed, but that does not mean the house was not pre plumbed for one. I include one when i build a house. Usually there is a return loop in the garage with a half inch drain line protruding out from the wall.
Now that makes sense. There is no water softener or any other equipment other than water heater in garage. There is a loop in the garage with a shutoff valve. The drain coming down from the attic in a second story just made no sense. So we learn something new everyday. Pre plumbed for water
softener would almost have to be it.