Bath sink had a extra drain line. I have never seen this before. Any help appreciated.
That’s a good one Greg, never seen that either.
Hope someone has and what it is for. 
Was it incorrectly connected to condensate drain?
Never seen one either, but reminds me of an air gap.
Kinda looks like it, doesn’t it?
Thats what the buyer thought. But it is not part of the condensation line.
A closet was on the other side of the wall and there was no drywall patches on the wall, so it must have been original.
Appears to be connected to a PVC line.
This was most likely a slab right. So you can’t see where the discharge went too?
TPRV drain ??? :shock::shock:
Did “Meeker Industries” work on it?
Was there a water softener anywhere
Basement drain primer. who knows?
Was it vented?
Was the kitchen on the other side?
Yes it is a slab on grade. The copper connects to pvc before it enters the wall. There is no other plumbing in the area other than the bathroom.
You do realize a basement in FL is not a good idea don’t you. 
Around here, a basement is also known as an indoor pool.
By the looks of it, I would have assumed it to be an improperly connected condensate drain line, or a poorly designed trap-primer (both of which have already been mentioned). In any event, it needs “further investigation” to determine its purpose and remedy.
I would suspect a homeowner / Dutch Uncle fix to a nuisance clogging P trap. The drain tail stock is on the outside of the lower section (wye) and is not threaded (or least I have never seen one threaded on the insides), the whole thing looks like some kind of bypass that ties back into the drain and / or vent inside the wall. Of course a bypass defeats the main purpose of the P trap and allows sewer gas back into the home. The material the Wye fitting is made of is all wrong as well and most likely not even normally used for residential plumbing. Some cobbled together PoS. I will give them a high five on ingenuity but an “F” on design principle.
I did a large home on one of the many back bayous here owned by a sea captain that worked offshore for the oil companies. He had more strange crap; fittings, electrical switches, valves that just one look said “borrowed” from the oil rigs and or his boat. It was set up like a boat too…water valves in the garage overhead, redundant electrical switches. Creative but crazy as hell. Needless to say the buyers walked…
Greg…
Did you ever figure out what this is/was???
Most likely a floor trap primer in Vero Beach, FL.